492 



SCIENCE 



[N. S. Vol. XXV. No. 639 



The function of the pancreatic secre- 

 tion seems to be an instance in which me- 

 chanisms of a different type are sharing in 

 its management. It has long been estab- 

 lished that the pancreatic secretion stands 

 under the influence of the central nervous 

 system. Recently it was discovered by 

 Bayliss and Starling that an intravenous 

 injection of secretin causes a considerable 

 increase of pancreatic secretion. Secretin 

 is an extract made of the duodenal mucosa 

 with an addition of hydrochloric acid. It 

 is assumed that this substance is produced 

 normally when the acid chyme comes in 

 contact with the mucosa of the duodenum, 

 and that by its absorption into the circula- 

 tion it is one of the normal causes of 

 pancreatic secretion. Now the effect of 

 the secretin seems to have nothing to do 

 with the nervous system, since the injection 

 is active even after all connections with 

 the nervous system are destroyed. On the 

 other hand, in cases of aehylia gastriea, in 

 which the stomach is devoid of all secre- 

 tion, the pancreatic secretion is apparently 

 normal, as the digestion of proteids re- 

 mains undisturbed. But since in these 

 cases there is no secretion of hydrochloric 

 acid, secretin ought to be absent; here the 

 pancreatic secretion is probably attended 

 to properly by the other partner in the 

 management of the function, that is, by the 

 central nervous system. 



A double management of partners of a 

 different type exists probably also for the 

 mammary secretion. There is sufficient 

 evidence that the secretion of milk is under 

 the influence of the nervous system. 

 Nevertheless, the secretion continues after 

 all nerves going to the mammary glands 

 are cut. The milk secretion in the latter 

 case is probably kept up by a stimulation 

 through an internal secretion provided by 

 the reproductive organs. Internal secre- 

 tion is probably a coexisting factor in 

 many functions of the body. 



Furthermore, there are instances in 

 which one function is cared for by two 

 separate organs. The function of diges- 

 tion of proteids in the alimentary canal is 

 carried on by two separate organs with a 

 different chemical activity: the pancreas 

 and the stomach. The trypsin of the pan- 

 creas digests proteids in an alkaline me- 

 dium, while the pepsin of the stomach is 

 active only in an acid medium. 



An arrangement of a similar character 

 we meet with in the organization of the 

 function of the defence of the body carried 

 on by the white cells against foreign in- 

 vaders. This cellular army of defense is 

 made up of two types: the microphages, 

 the polynuclear leucocytes whose abode is 

 in the bone marrow; and the macrophages, 

 the large mononuclear cells which have 

 their barracks in the lymph nodes and 

 lymphoid tissue. According to Opie one 

 of the effectual weapons of these warriors 

 is their intracellular proteolytic ferments. 

 But the ferment of the microphage is active 

 in an alkaline medium, while that of the 

 macrophage requires for its activity an 

 acid medium. 



As factors of safety we may consider 

 also the assistance which one organ lends 

 to another or the vicariation of one organ 

 for another. For instance, the assistance 

 which the sweat glands render to the kid- 

 ney in the process of elimination of a sur- 

 plus of water, or the vicariation of the 

 mucous membrane of the intestinal canal 

 in the process of elimination of urea. Such 

 mutual assistance of the organs is a wide- 

 spread institution in the animal body and 

 assures the safety of many vital functions. 



Returning to the organs which are pro- 

 vided with a large surplus of active tissue, 

 the question confronts us: which is the 

 mode of distribution of the normal activity 

 of an organ among its luxurious tissues? 

 Since the activity of such organs, as we 



