1 8 INTERNAL SECRETION 



plays the part of determining factor. Instances are afforded by 

 the operative treatment of Graves 's disease and the extirpation of 

 pituitary tumours in acromegaly. 



Experimental pathology has reached a high stage in its 

 development and experiments upon animals have done much to 

 clear up the mystery which surrounds the internal secretory 

 processes. 



Addison's discovery supplied the incentive to the first orderly 

 experiments on living animals. It was thought that the 

 extirpation or destruction of the suprarenals would not only throw 

 light upon the pathogenesis of Addison's disease, but would also 

 help to an understanding of the physiology of the organs them- 

 selves. The experimental extirpation of various organs has, in 

 the first place, decided their indispensability to the life of the 

 organism. In the second place, from symptoms arising after the 

 suppression of any organic function, the most certain knowledge 

 regarding the normal activity of that organ has been deduced. 

 The internal secretory function of the pancreas, which plays a 

 very important part in the economy, was discovered by means 

 of experimental extirpation by v. Mehring and Minkowski. Quite 

 recently, the removal of the pituitary body of animals has supple- 

 mented to a remarkable degree the observations of pathologists in 

 regard to its function. 



Extirpation experiments with animals have certain advantages 

 over pathological destruction in man. In the first place it is 

 possible to choose a subject suitable for experiment; and in the 

 second, it is possible to localize exactly the destructive process, 

 even to a single portion of a single tissue. It is to this that 

 we owe the discoveries which have been made concerning the 

 function of the parathyroid glands. The value of the method, 

 when employed on different species of animals, will appear later 

 when we are dealing with the suprarenal system. 



Another method, that of the destruction of certain tissue 

 elements by means of cytotoxic sera, has not fulfilled all that 

 was expected of it. The method is based upon the experiments 

 of Bordet, Landsteiner, Ehrlich and Morgenroth. These 

 observers found that, if an animal is treated with the red blood 

 corpuscles of another species, substances the so-called hasmo- 

 lysins are formed in its serum which will dissolve, in vitro 

 and in vivo, the blood corpuscles of the species from which the 

 red blood corpuscles were taken. It was expected, therefore, that 

 treatment with either cells or organic extracts would induce the 

 formation of cytolysins (which correspond to the hasmolysins) 

 and of cytotoxins, and that these could be employed to bring 

 about by chemical means specific injury or complete destruction 

 of the organs. 



Acting upon this hypothesis, substances which were cytotoxic 

 to different organic cells were prepared, and this method of 



