356 THE INFLUENCE OF THE ORGANS ON ONE ANOTHER 



molecules, but only imperfectly so. Then an emigration of salt molecules and 

 immigration of water molecules will take place simultaneously. 



According to the foregoing, the least change in the osmotic pressure of a 

 single cell will result in a movement of substance of some kind. For a com- 

 plex of cells the currents of the individual cells will be added together if they 

 proceed in the same direction ; they will weaken or entirely neutralize each other 

 if they proceed in opposite directions. We must think of the entire organism 

 therefore as permeated by numberless currents and counter currents. Never 

 during life can there be a moment of complete equilibrium, and yet there is a 

 constant endeavor to reach this condition. Thus we might expect a priori what 

 is abundantly confirmed by experience, that the osmotic pressures of the different 

 fluids of the body are approximately the same though never exactly so. In the 

 same way the osmotic pressure of the same fluid will not always be uniform, 

 but will vary within narrow limits (Koeppe). 



2. INTERNAL SECRETIONS 



A. GENERAL 



The organs affect one another in many ways by means of their metabolic 

 products. Carried by the blood to all parts of the body, these products act either 

 to heighten or to reduce the activities of the other organs. 



The so-called automatic excitation (cf. page 52) by the action of decompo- 

 sition products of the organs on different parts of the central nervous system is 

 of vast importance in the regulation of the physiological activities of the body, 

 and is to be mentioned first in this connection (cf. also Chapter XXII). For 

 example, when by the activity of the digestive apparatus proteid in increased 

 quantity is thrown into the blood, and the proteid destruction in the body rises 

 as a consequence, the effect in all probability is due to the direct influence of 

 the proteid and its digestive products on the organs i. e., the activity of the 

 digestive apparatus has brought about an increase in the decompositions of 

 the body without the cooperation of the nervous system (cf. page 99). 



Various products of the decomposition of proteid formed in the different 

 parts of the body are carried by the blood to the liver and there are transformed 

 into urea (cf. Chapter XII). With more active destruction of proteid urea is 

 formed in larger amount and this according to our present information stimu- 

 lates the kidneys to increased activity (cf. Chapter XIII). 



The organs act upon one another not only by their katabolic products, but 

 also by substances formed synthetically in some organs, which, entering the 

 blood, profoundly influence the general bodily functions. Such substances, 

 the chemical nature of which is for the most part entirely unknown to us, 

 are formed by the testes, ovaries, thyroid gland, pancreas, and adrenal bodies, 

 probably also by the pituitary body and the kidneys. It is very likely that 

 such internal secretions (Brown-Sequard) are formed by other and perhaps 

 by all organs. 



Strictly speaking, the enzymes formed in the different organs belong here. 

 Since their importance for the general processes of the body has not been estab- 

 lished, we shall not consider them here, but shall merely refer to the facts already 

 cited at page 38. 



In the investigation of these internal secretions, workers have often been 

 content to test the action of organ extracts upon the body. This method of 



