History of the Preparation of Insulin - Homemade Insulin, Part 1….Did Eva Saxl mean Bergmann not Beckman ? Macleod's text

In the book, “Cheating Destiny: Living with Diabetes”, the author, James Hirsch recounts how Eva Saxl, an insulin diabetic and her husband, Viktor, managed to produce a homemade insulin using information from a medical text called “Beckman’s Internal Medicine”. They did this under duress in World War II in China during the Japanese occupation of Shanghai. Not only were they able to keep Eva alive with the homemade product but also another 200 diabetics in the Shanghai Ghetto where they lived.

Eva herself retold the story but with no mention of the Beckman’s medical text, shortly after the war, in the 50’s for Edward R. Murrow’s radio broadcast, “This I Believe.” - http://thisibelieve.org/essay/16957/   .  Eva Saxl died in 2002 in Santiago, Chile.

There do not appear to be any records showing such a medical text “Beckman’s Internal Medicine” ever existed either in English or German (Innere Medizin). What does exist are medical textbooks published by Bergmann in Munich at the same time. Especially notable was the volume, “Insulin”, by Grevenstuk and Laquer, published by Bergmann in 1925. The book was written in German. Eva was an accomplished linguist, fluent in 5 languages. It was referenced by J.J.R. Macleod a professor of physiology in Toronto and one of the prominent researchers involved the development of Insulin, in his book “Carbohydrate Metabolism and Insulin”, published in 1926 by Longmans, Green, and Co. Ltd. of London.

What follows are excerpts from Macleod’s book for information purposes only and are intended only to relate to the story of the historical development of Insulin.

Chapter V. The History of the Preparation of Insulin.

 Page 65

“….In view of the large amount of work which had previously been done in the field, it was considered advisable to make certain of the anti-diabetic effects of the extracts, as judged by the behaviour of blood and urinary sugar, before proceeding to investigate their influence on other symptoms of diabetes, such as glycogen formation, ketosis, and changes in respiratory metabolism. The difficulty at this stage was to obtain adequate supplies of extract, so that Banting and Best devoted their attention mainly to this problem. With this object in view,⁽²⁾  they made use of the foetal ox pancreas, since it had been shown by Ibrahim that up to four months the acini are not sufficiently developed to secrete active trypsin, although the islets are abundant. Pancreases from foetal calves were therefore extracted, either with Ringer’s solution or with alcohol, which was then removed from the extract by evaporation in a current of warmed air, and the residue redissolved in Ringer’s solution. Decided anti-diabetic effects could readily be demonstrated by these extracts, and this suggested the attempt to make them from the pancreas of full-grown cattle, by extraction with equal volumes of 95 per cent. alcohol made slightly acid with HCL. This extractive was used with the object of minimizing the destructive action of the proteolytic enzymes, and its possible value in the preparation of insulin, previously suggested by Zuelzer and Scott, had been in mind from the very start of the investigations. After the removal of the alcohol, by warmed air, and of excess fat, by toluene, the extracts were found to possess strong anti-diabetic properties, and it was now possible to show, beyond doubt, that by continuous injections, a great improvement occurred in the general condition of the animals, one of which lived for seventy days, when it was killed by chloroform.”

Page 66

“On gross examination, no trace of the pancreas could be found, but serial sections of the duodenum, made by Dr. W.L. Robinson, revealed the presence in the submucous coat, near the entry of the main pancreatic duct, of a small nodule in which, however, no islets could be seen.

              An endeavour was now made to purify the alcoholic extracts of adult pancreas sufficiently for trial on diabetic patients. The alcohol was removed by warmed air, or in vacuo  at a low temperature, the excess of the fat extracted by toluene, and the watery residue, now reduced to one-fifth the original volume, was passed through a Berkefeld filter. The resulting extract, injected into a diabetic patient (a boy aged fourteen years), lowered the blood sugar by a little over 25 per cent., and somewhat diminished the glycosuria, but “owing to the high percentage of protein … sterile abscesses formed in a few instances at the site of injection.” Banting and Best ⁽³⁾ stated that the potency of their extracts was destroyed by heat and by digestion with trypsin, and that the active principle was insoluble in 95 per cent. alcohol.

              Before further attempts could be made to investigate the possible therapeutic value of the extracts, it was necessary to remove from them the irritating substances responsible for abscess formation, and to demonstrate, in diabetic dogs, not only that the hyperglycaemia and glycosuria by their action, but also that the other diabetic symptoms are removed. At the same time, it was considered important to see whether other forms of experimental hyperglycaemia, such as that caused in rabbits by piqu ^{^}re or epinephrine, would be affected by the extracts.

              The problem of purification was entrusted to J.B. Collip, who, as a first step in his work, injected some of the crude extract into normal rabbits, and found the blood sugar to become reduced. This furnished him with a method for testing the potency of the various precipitates and filtrates which were produced in the crude alcoholic extracts by various strengths of alcohol. He finally found that the active principle remained in solution up to an alcohol percentage of about 92, and that by using percentages somewhat below this, much of the protein could be precipitated from the extracts.

              While this work was in progress, in Toronto, a paper by”

Page 67

“Paulesco came to our notice, and after it was completed, one by Gley.

              Paulesco’s researches were communicated at a meeting of the Reunion Roumaine de Biologie in the spring of 1921, when he described the effects produced by intravenous injections of sterile pancreatic extracts on the percentage of sugar, of acetone bodies, and of urea in the blood and urine of depancreatised dogs. Typical observations are shown in Table II. :---

              There can be no doubt that all three substances became markedly reduced in amount, in both blood and urine, as a result of the injections. The results were the same whether the injection was made into a branch of the portal vein or into the jugular vein. The effects were noticeable in one hour following the injection, attained their maximum in two hours, and passed off in twelve hours. They varied with the amount of gland present in the injected extract. Paulesco also observed that the blood sugar, as well as the blood urea, in a normal dog became lowered by the injections. It is evident that some error must have been incurred in the measurement of the blood sugars, the value for normal dog blood being given as 0.044 per cent., and for the same animal, two hours after the injection, as 0.028 per cent. At such percentages violent hypoglycaemic symptoms would have been manifest. The highest blood sugar recorded”

Page 68-69

“after pancreatectomy is 0.27 per cent. No observations are recorded of the behaviour of the respiratory quotient or of the glycogen content of the liver, and no evidence is given that the general symptoms of diabetes were lessened, or the life of the animal prolonged….”

Bibliography …. (selected)

             

…. Banting, F.G., and Best, C.H. ⁽¹⁾ “ Jour. Lab. & Clin. Med., “1922, vii, 251.⁽²⁾  “Jour. Lab. & Clin. Med., “ 1922, vii, 464.⁽³⁾  “Trans. Roy. Soc. Canada, “Sec. V., 1922, xvi, 27. ….

Chapter VI. The Preparation and Chemical Properties of Insulin.

Page 70

“Since a method suitable for the manufacture of insulin on a large scale was first described, numerous modifications have appeared, some of them involving principles essentially different from those upon which the original method of Collip depends. Without entering into details with regard to the various problems of chemical technique and engineering which are involved, a brief outline of the more important large-scale methods may be of interest. An excellent detailed description of the published methods will be found in the article by Grevenstuk and Laqueur.

The Method Elaborated by Collip. –

              Freshly minced pancreas is allowed to stand, with occasional stirring, for a few hours with about an equal volume of 95 per cent. ethyl alcohol, after which it is strained through cheese cloth and the extract filtered through paper. Sufficient alcohol is then added to the filtrate to bring the percentage of alcohol to about 60, when, on standing, the major part of the protein separates out, and is removed by filtration. This second filtrate is concentrated to small bulk, by distillation in vacuo at a low temperature, and fat and other lipoid substances are removed, partly by skimming and partly by extraction with ether in the separating funnel. The purified extract is returned to the vacuum still and concentrated until of a pasty consistency, when alcohol is added so as to give a total percentage of 80. The mixture is centrifuged, whereby an upper layer consisting of alcohol containing the active principle in solution separates out. This is pipetted off and the insulin precipitated by throwing it into several volumes of absolute alcohol.  After standing some hours this precipitate is collected on a Buchner funnel, dissolved in distilled water, and the solution passed through a Berkefeld filter. After the resulting insulin is sufficiently free of impurities so that it can be used for repeated clinical administration it is, nevertheless, coloured and contains a considerable percentage”

Page 71

“of inorganic salts and of protein.¹  Various methods have, therefore, been suggested for its further purification, the best known being those of Doisy, Somogyi, and Shaffer, and of Dudley.

The Method of Doisy, Somogyi, and Shaffer. –

              The alcohol with which the initial extractions are made contains 20-30 c.c. con. H₂SO₄ for each kilogram of pancreas, and the first extraction, after removal of the alcohol in the vacuum still or in a current of warmed air, is mixed in a separating funnel with ammonium sulfate in the proportion of 40 grams to each 100 c.c. of solution. After standing at a low temperature, a precipitate rises to the surface and sticks to the walls of the funnel. Since this contains the major part of the insulin, the liquid under it is drained off, the precipitate dissolved in water, reprecipitated with (NH₄)₂SO₄, and finally dissolved in water containing sufficient ammonia to bring the pH to between 6 and 8. By centrifuging, a clear watery extract is obtained, to which weal acetic acid is added, so as to bring the pH to about 5. After standing at a low temperature for some hours, the precipitate which forms is collected and redissolved in water containing sufficient acid (HCl) to bring it into solution. The insulin is then reprecipitated by readjusting the pH to between 5 and 6, and the final precipitate collected on a filter and dried in a vacuum desiccator. From this dried material insulin of any desired strength can then be prepared by dissolving in weak acid.

The Method of Dudley. –

              Insulin, prepared by Collip’s process, is dissolved in a small quantity of water and the solution centrifuged, so as to free it from insoluble material. The supernatant fluid is then diluted with water to bring the concentration of the original crude insulin to about  1.5 per cent. pH adjusted to about 5, half the volume of a saturated watery solution of picric acid added,  and the mixture allowed to stand some days in a tall vessel. By this time a yellow precipitate settles out (insulin picrate), and the supernatant fluid is removed by decantation, the precipitate being dissolved at a low temperature in a minimum of water containing weak sodium carbonate. From this solution the insulin picrate is reprecipitated by neutralizing with acid, some more saturated picric acid solution being added to ensure complete precipitation. After standing some days this second precipitate is collected on a Buchner funnel and thoroughly washed with weak picric acid solution, then transferred to a beaker and stirred with a solution of HCl in 75 per cent. alcohol. The correct proportion of HCl is obtained by”

“¹ It was found advantageous, when trying to develop this method on a large scale, to use 95 per cent. acetone in place of alcohol for the first extraction and to make this faintly acid by means of acetic acid (0.1 per cent.). Evaporation in a warmed air current was used instead of the vacuum still, one advantage being that the fats separated out readily. The concentrated extract (about one-tenth the original volume) was then treated with alcohol, as recommended by Collip (cf. Best and Scott).”

Page 72

“taking 25 c.c. of 3 N  HCl in 75 c.c. absolute alcohol. On mixing the acid alcohol with the picrate thick, dark brown, oily drops are first formed. These afterwards dissolve, by stirring, in the acid alcohol, to form a slightly turbid, yellow liquid. By the addition of about ten volumes of pure acetone, insulin hydrochloride precipitates out from this solution and is collected on a filter, washed with acetone, and finally with ether, until all traces of picric acid are removed. After drying in a vacuum desiccator, a white powder of tolerably constant composition and strength is obtained. It should be kept in a sealed tube, or over P₂O₅ in a desiccator.

              A few of the modifications of these original methods may be alluded to. Krogh and Hagedorn have considerably increased the yield obtainable from ox pancreas by freezing the freshly removed glands. The blocks of ice are then cut by rapidly revolving knives into very thin shavings which are collected in acidified alcohol (pH 2). The reaction of the alcoholic extract is then readjusted to pH 4.6 by means of lime, and after reductions in volume the insulin is purified by means of (NH₄)₂SO₄. The solution of crude insulin is boiled for two minutes at a pH below the isoelectric point, so that Berkefelding is dispensed with.

              Brailsford Robertson, and Anderson have considerably cut down the amount of alcohol required in the original process by using exsiccated sodium sulphate. They add to the first 50 per cent. alcoholic extract of the pancreas sufficient sulphate to remove four-fifths of the water present, thereby raising the percentage of alcohol in the mixture to about 80, at which concentration protein fractions not containing insulin are precipitated.

              Several papers have appeared from time to time by Murlin and his co-workers describing various methods for the preparation of insulin. The most approved method consists in preserving the pancreas in chilled 0.2 per cent. HCl and then, after mincing, heating it (to 75⁰ C.) in 4 volumes of acid of this strength for an hour. After chilling the fat is skimmed off and the mixture is strained through cheese cloth. The pH is then adjusted to 4.9, the solution is filtered through coarse filter paper, and 250 gms. NaCl is added to each 1000 c.c. of filtrate. The precipitate which settles out contains all of the insulin, as well as some protein. The insulin is dissolved out by 70 per cent. alcohol, and the alcoholic extraction shaken with 3-5 volumes of amyl alcohol and centrifuged. A precipitate forms between the aqueous and alcoholic layers. It is dissolved in 80 per cent. alcohol, filtered, and the alcohol removed by evaporation in vacuo. A watery sterilised solution of the residue is insulin. For the preparation of a form of insulin which gives no biuret test the authors recommend using perfusates obtained by circulating 0.2 per cent. HCl through the blood vessels of the excised pancreas. The pHof the perfusate is adjusted to pH 5.85, at which metaprotein is thrown down. After filtering, pH is adjusted to 4.1 and NaCl added ( 1 gm. To 3.5 gms. pancreas), after which the fluid is evaporated to dryness and the residue repeatedly treated with 80 per”

Page 73

“cent. alcohol. After removal of the alcohol by evaporation the residue is treated with sterile water and pH adjusted to 4.1.

              Moloney and Findlay attained considerable success in the purification of insulin by taking advantage of the fact that it is adsorbed by benzoic acid when this is caused to separate out by adding mineral acid (HCl) to a mixture of crude insulin solution and sodium benzoate. These workers have also made detailed studies of the extent to which insulin is adsorbed by other agents, such as charcoal, but the methods are not economically applicable on a large scale.

              Through the work of Best and Scott and their collaborators in the Connaught Laboratories of the University of Toronto, and of Clowes, Walden and others in the laboratories of Eli Lilly and Company of Indianapolis, numerous details of practical value have been elaborated and applied in the manufacture of insulin.

The Method of Dodds and Dickens. –

              This is a modification of the method of Dudley, with the difference that picric acid is directly mixed with the pancreas, instead of with crude insulin as prepared by Collip’s process. As a matter of fact, the use of picric acid as the first step had been suggested by Dudley for the preparation of insulin from the principal islets of fishes prior to its use by Dodds and Dickens for mammalian pancreas. The process is relatively simple and should be less costly than the older ones. The chilled, fat-trimmed pancreas is passed through a mincing machine along with finely powdered picric acid and the process repeated several times. The picric acid unites with insulin to form the picrate, which is then leached out from the yellow paste by the addition of sufficient acetone to give a concentration of 70 in the mixture, and thorough trituration. The acetone extract is filtered through cloth under a press and extraction repeated several times with 70 per cent. acetone. The acetone is removed from the clear combined extracts by evaporation in vacuo, and the mass of picrate, fats, and picric acid crystals which remains is transferred to a Buchner funnel on which it is rubbed up with ether, which is then sucked through, this process being repeated until all fats and picric acid have been removed. The picrate is then converted into hydrochloride by the Dudley process (p. 71).

              As a method for the preparation of insulin from the principal islets of fishes, this method, as originally used by Dudley, is very satisfactory, especially since the islets can very conveniently be preserved in moistened picric acid, in place of alcohol. The only precaution to observe is that the islets should be crushed and stirred in among the picric acid crystals, otherwise sufficient penetration does not occur to prevent deterioration. We found this to our cost in a large amount of islets removed from halibut (Pseudopleuronectidae). The islets, which are large and very accessible in this fish, were merely dropped into a saturated solution of picric acid, but in several weeks’ time, when they reached the laboratory, they were found to have decomposed, so that only traces of insulin were obtained.”

Page 74

The Chemical Properties of Insulin. –  The majority of investigators consider insulin to be closely related to proteose (Dudley, 1923). In a general way, it is true that it closely resembles this protein in most of its reactions, but in many of them so faintly so that the possibility remains that insulin is a non-protein substance which for some reason remains attached to proteose, even after such chemical treatment as would be expected to rend them apart. It is really impossible to say what insulin is, for there is no reason to believe that it has yet been isolated, even in a tolerably pure state, and until this is accomplished, it can be of little interest to review the numerous chemical properties which have been ascribed to it.

              In what is probably the purest form, as prepared by isoelectric precipitation, insulin exists as a white powder, of which from 0.015 – 0.025 mg. corresponds to one unit (p. 242), and it contains 13 – 17 per cent. of nitrogen, no phosphorus, but considerable sulfur. The activity is often greater in preparations containing the least nitrogen (Matill, Piper, Kimbal and Murlin). It dissolves with difficulty in strictly pure water, but readily so in a trace of acid or alkali. It is precipitated within a certain range of pH, the exact limits depending upon the purity of the preparation, as well as on the nature of the solvent and the presence of electrolytes. In pure water it precipitates in the presence of strong acid, remains in solution between ph 2 and 4, precipitates again between ph 4.3 and 5.7, and remains in solution beyond ph 6 (Doisy, Somogyi, and Shaffer).

              Insulin prepared from the pancreas of the skate, by the relatively simple process of extraction with about 60 per cent. acidified alcohol, and subsequent heating of the alcohol-free extract, failed to show any precipitation by adjustment of the reaction (Best and Macleod). In the presence of small concentration of salts, especially sulphates, the isoelectric point shifts towards the acid side, and precipitation may occur at pH 4, or even less, and when much salt is present, such as 1/3 to ½ saturation with (NH₄)₂SO₄, or saturation with Na₂SO₄ or NaCl, insulin may become precipitated well below this level of pH. A multitude of other salts also precipitate insulin, as well as such reagents as picric acid, trichloracetic acid, etc. (cf. Widmark).

              Insulin is soluble in ethyl alcohol up to a concentration of 80 per cent. provided the reaction is outside the isoelectric range, this being the”

Page 75

“basic fact upon which Collip, developed his method of purification. At this concentration of alcohol, most protein substances are precipitated, and trypsin fails to develop its digestive properties. It is said that within the isoelectric range insulin is more soluble in weak alcohol than in water (Grevenstuk and Laqueur). Insulin is also soluble in methyl alcohol and in glacial acetic acid, phenol, formamid, and the cresols. It is insoluble in alcohol above 90 per cent. and in the fat solvents. In this regard, however, it should be stated that insulin prepared from fish pancreas (skate) gave no precipitate, even when a watery solution was dropped into absolute alcohol. With regard to other physical properties, the apparently purest preparations of insulin have all been found to be readily adsorbed, especially in acid solution, by kaolin, charcoal, benzoic acid, and Lloyd’s reagent. This made it difficult, in the earlier stages of manufacture, to avoid serious loss of insulin while sterilising the solutions by passing them through the Berkefeld filter, but Dudley has shown that this loss can be entirely prevented by adjustment of the reaction to ph 7.5. It is also possible to decolorise insulin solutions by means of charcoal provided the reaction be properly adjusted (Krogh and Hagedorn, private communication). Moloney and Findlay have made a careful study of the adsorption properties of insulin, and have suggested a method of purification based upon them.

              In numerous attempts to dialyse insulin through parchment or collodion sacs, no trace was ever found by us to pass out, but more recently Shonle and Waldo have succeeded. Dingemasse (cf. Grevenstuck and Laqueur) has been unsuccessful in demonstrating any dialysis of insulin. He attempted, by this method and also by that of electrodialysis, to separate insulin from traces of protein.

              Contrary to the earlier findings of Banting and Best (p. 66), insulin readily withstands heat, at least when in faintly acid solution (pH 4 or less). We have, for example, kept a faintly acid solution of insulin actively boiling under a reflux condenser for two hours without being able to detect any deterioration in potency. At reactions above pH 5, however, insulin is destroyed by heat, the more rapidly the more alkaline the solution. Properly prepared solutions can withstand moderate temperatures, as would be met with in the tropics, without any loss of potency, although in some preparations sent to the testing laboratories of the Insulin Committee, a certain cloudiness, accompanied by loss of potency, has been observed to become developed, by keeping them at about 50⁰ C. for ten days. The instability of insulin in the presence of alkali is of interest, and has been systematically investigated by Witzemann and Livshis. By standing at room temperature for six days in the “

Page 76

“presence of 0.5 N . NH₄OH, insulin all but loses its potency, which, however, gradually returns if the solution be made acidic again, which has led these investigators to suggest that some tautomeric change occurs in the insulin molecule. Alkaline phosphates and carbonates do not appreciably affect the strength of insulin, even on prolonged standing at room temperature.

              The proteolytic enzymes rapidly inactivate insulin (trypsin, pepsin, papain, and erepsin), and it is generally believed that this is because it is destroyed. Epstein and Rosenthal have, however, made the statement that this is really not the case, but that the insulin merely becomes inactivated, and that its potency can be restored by raising the acidity of the solution. They state that this inactivation occurs promptly when trypsin is added to insulin in faintly alkaline reaction in vitro, and that it occurs in vivo when trypsin is injected along with insulin. They draw far-reaching conclusions regarding the role that such a combination occurring in the body must have in the aetiology of diabetes. But other investigators have failed to corroborate their results, and they seem, inherently, to be highly improbable.

              An attempt to reduplicate them in my laboratory (by Macela) seemed, at first, to be successful, but not so when regard was taken of the behaviour of insulin towards weak alkali. As a matter of fact, insulin in the presence of weak alkali and trypsin seems to be rapidly and permanently destroyed, which is the basic fact upon which depended the conclusive demonstration (by Banting and Best) of its presence in pancreatic extracts.

              It is possible that insulin may exist in the cells of the islets of Langerhans as some inert compound prior to its secretion into the blood, or at least as some precursor which is activated during the process of extraction, but it is highly improbable, as has been suggested by Epstein and Rosenthal, that trypsin plays any role in this connection.

              Much attention has been paid as to whether or not insulin gives the colour reactions for proteins. When insulin from the ox or pig pancreas is used, the biuret test is invariably obtainable, although I have failed to observe it in insulin prepared from the pancreas of skate (Raja), and Murlin and his collaborators have failed to obtain it in ox insulin prepared by them (p. 72). This may merely mean that the biuret test is not sensitive enough. Doisy, Somogyi, and Shaffer still obtained this reaction, as well”

Page 77

“as that of Millon, and Dudley is emphatic that it always occurs. With regard to the other colour reactions, there is much division of opinion, and an excellent summary of the findings will be found in the article by Grevenstuk and Laqueur. Until insulin can be prepared in greater purity, however, it is useless to place any weight on these reactions. The suggestion has been made that insulin may be related to guanidine (Sjollema and Seekles (cf. Grevenstuk and Laqueur)). J.J. Abel and his co-workers have recently succeeded in obtaining insulin in crystalline form.”

Bibliography.

Allen, Piper, Kimball and Murlin. “Proc. Soc. Expt. Biol. and Med.,” 1923, XX, 519.

Best and Scott. “Jour. Biol. Chem.,” 1923, lvii, 709.

Best and Macleod. “Amer. Jour. Physiol.,” 1923, lxiii, 390.

Collip, J.B. Cf. Banting, Best, Collip; and Macleod, “Trans. Roy. Soc. Canada,” 1922, xvi, 28.

Doisy, Somogyi, and Shaffer. “Jour. Biol. Chem.,” 1923, lv, Proc. xxxi.

Dudley. “Biochem.  Jour.,” 1923, xvii, 376.

Dodds and Dickens. “Brit. Jour. Expt. Path.,” 1924, v, 115.

Epstein and Rosenthal. “Jour. Amer. Med. Assoc.,” 1924, lxxxii, 1990.

Grevenstuck and Laqueur. “Insulin.” Bergmann, Munchen. 1925.

Krogh. Private communication.

Kimball and Murlin. “Jour. Biol. Chem.,” 1923, lviii, 337.

Murlin, Clough, Gibbs, and Stokes. “Jour. Biol. Chem.,” 1922, lvi, 253.

Moloney and Findlay. “Jour. Biol. Chem.,” 1923, lvii, 359.

Matill, Piper, Kimball, and Murlin. “Quart. Jour. exp. Physiol. Suppl.,” 1923, xiii, 182.

Piper, Allen, and Murlin. “Jour. Biol. Chem.,”  1923, lviii, 321.

Robertson, T.B., and Anderson. “Med. Jour. of Australia,” 1923, ii, 189.

Shonle and Waldo. “Jour. Biol. Chem.,”  1924, lviii, 731.

Widmark. “Biochem. Jour.,” 1923, xvii, 668.

Witzemann and Livshis. “Jour. Biol. Chem.,”  1923, lvii, 425; and ibid., lviii, 463.

History of the Preparation of Insulin - Homemade Insulin, Part 5….Did Eva Saxl mean Bergmann not Beckman ?