August 4, 1905.] 



SCIENCE. 



135 



terest, as these acids must represent degen- 

 erative or otherwise abnormal products 

 having- their origin in the liver and other 

 organs. 



Unquestionably one of the most impor- 

 tant fields of effort in physiological chem- 

 istry at the present time is the study of the 

 soluble ferments, and we have here for con- 

 sideration not only certain newly discov- 

 ered enzymes, but, perhaps, of more im- 

 portance, a great advance in our knowledge 

 of those already known. It was not many 

 years ago that we considered the question 

 of the gastric enzymes as practically set- 

 tled. The presence of both pepsin and 

 rennin no one could have doubted, but the 

 work of Pawiow and his school in the last 

 five years has thrown entirely new light on 

 the subject and it would appear that one 

 and the same ferment, working under dif- 

 ferent conditions, is responsible for both 

 classes of observed phenomena. Pawlow 

 has compared the digesting and milk curd- 

 ling power of ferment secretions from the 

 true pepsin and pyloric glands of the 

 stomach, from the pancreas and from Brun- 

 ner's glands, and has found them perfectly 

 parallel under proper conditions of experi- 

 ment; any cause which operates to destroy 

 one power, destroys also the other according 

 to Pawlow. But in any given extract or 

 preparation the conditions must be prop- 

 erly chosen to show both effects. A com- 

 mercial rennet, for example, may exhibit 

 the milk curdling action very strongly, yet 

 appear to be wholly inert toward fibrin. 

 Pawlow holds that in all such cases simple 

 dilution with very weak hydrochloric acid 

 is all that is called for to show the peptic 

 power. A valuable resume of this w^ork 

 is given in a recent number of the Zeit- 

 schrift fiir physiologische Chem. (Vol. 42, 

 p. 415, 1904). 



It is proper to say that the physiologists 

 of the Hammarsten school do not admit the 



claims of Pawlow, although the doctrines 

 of the latter have been put in very strong 

 light. 



To Pawlow we owe, also, the discovery of 

 a new group of ferments which he calls 

 kinases, or activators. The most thor- 

 oughly studied of these is the enterokinase 

 which converts the inactive pancreatic juice 

 into an active ferment secretion. As to 

 the value of the other kinases much less is 

 known. 



About four years ago Cohnheim de- 

 scribed, under the name of erepsin, a pecu- 

 liar ferment in the intestinal walls w^hich 

 has the power of splitting peptones and 

 proteoses, but not albumins. This discov- 

 ery grew out of an investigation to deter- 

 mine the fate of the peptone bodies of 

 proteolysis, it being long known that no ap- 

 preciable amount of these substances ap- 

 pears in the circulation after digestion. A 

 theory grew up to the effect that in the 

 intestinal walls, just before absorption, 

 they were converted back into true albu- 

 mins. According to the views now ad- 

 vanced by Cohnheim and others this can 

 not be the case to any large extent. The 

 peptones break down with liberation of the 

 carbon and hydrogen excess, which serves as 

 a source of energy, while the nitrogen frac- 

 tions go over into the form of amino acids, 

 to be further broken down by the liver. 

 This coincides with the view that very little 

 protein is actually needed by the body. On 

 the other hand, it is held by several physiol- 

 ogists that the erepsin katabolism does not 

 go so far, but merely to the production of 

 amino compounds which are ready for a 

 synthesis not yet understood. 



If time permitted I should like to go 

 into the question of enzymes in other direc- 

 tions, especially with reference to the work 

 in the liver and the action of the so-called 

 autolytic ferments, the behavior and gen- 

 eral importance of which are still very ob- 



