376 THE POPULAR SCIENCE MONTHLY. 



the discovery that peptones prevented the coagulation of the blood in 

 dogs, and the latter, under Ludwig's direction, has also investigated 

 their action upon the circulation. He finds that, when injected into a 

 vein, they greatly depress the circulation, so that the blood-pressure 

 falls very considerably ; and when the quantity injected is large, they 

 produce a soporose condition, complete arrest of the secretion by the 

 kidneys, convulsions, and death. From these experiments it is evident 

 that the normal products of digestion are poisons of no inconsiderable 

 power, and that if they reach the general circulation in large quantities 

 they may produce very alarming, if not dangerous, symptoms. 



Such experiments as this open up a new and very wide field of in- 

 quiry, which is likely to prove of very great practical importance. We 

 have hitherto been accustomed to reckon all peptones as identical, by 

 whatever digestive ferment they were formed, and to look upon it as 

 a matter of slight moment whether albuminous foods introduced into 

 the digestive canal were dissolved by the stomach or by the pancreas, 

 although it is quite possible that the peptones differ as much from each 

 other as different kinds of sugars. It is a matter of wonder, also, that 

 at the present moment, although the digestive processes have been so 

 carefully investigated, we know very little of the uses of the succus 

 entericus. Notwithstanding the great extent and evident importance 

 of the intestine, and the large quantity of fluid which it is able to se- 

 crete, all that we find regarding the action of this secretion in such a 

 book as Foster's " Physiology " is that " the statements with reference 

 to its action are conflicting. Probably it has no direct action on either 

 fats or proteids, but is amylolitic in some animals, though not in all." 

 Succus entericus has also been said to change cane- into grape-sugar, 

 and by a fermentative action to convert cane-sugar into lactic acid, 

 and this again into butyric acid, with an evolution of carbonic acid 

 and free hydrogen. The reason why experiments on the action of 

 intestinal juice have given such an apparently unsatisfactory result 

 is that they have been chiefly tried on such kinds of food as we are 

 accustomed to put into our mouths. Now, the intestinal juice is not 

 intended to act upon such substances : its place is to finish the diges- 

 tion begun by the other juices ; and when experiments with intestinal 

 juice are tried upon foods which have previously been subjected to the 

 action of the other digestive fluids, positive and not negative results 

 are obtained. Thus, for example, it was stated by Kiihne, in his lec- 

 tures at Amsterdam in 1868-69, that though intestinal juice would 

 dissolve raw albumen and fibrine, it would not act at all upon them if 

 boiled ; but if the boiled albumen or fibrine were first subjected to the 

 action of pancreatic juice for a short time, the intestinal juice would 

 afterward dissolve them much more quickly than it would even in a 

 raw condition. The action of digestive ferments is just beginning to 

 find a practical application in medicine, and sometimes, undoubtedly, 

 they are of very great service ; but unless their action is investigated 



