ON VARIATIONS. 359 



and here again the injection of extracts may delay the 

 fatal issue. Extirpation of the pancreas causes the 

 production of severe diabetes, and ultimately death, 

 but such an effect may be avoided by the grafting of a 

 portion of excised gland in the peritoneal cavity or the 

 tissues. In such a case it cannot, of course, exercise 

 its digestive function, but its internal secretion pre- 

 vents the onset of the fatal diabetes. Again, extirpa- 

 tion of the total kidney substance of a dog leads, not 

 to a diminished secretion of urine, but to a largely in- 

 creased secretion, accompanied by a rapid wasting away 

 which soon ends fatally. Hence the kidneys may pos- 

 sess an influence on the metabolism of the whole body, 

 as well as their obvious secretory function. The 

 spleen appears to have an internal secretion which 

 is of influence in setting free the pancreatic ferment. 

 Finally, extracts of various nervous tissues, brain, 

 spinal cord, and sciatic nerve, have been found when 

 intravenously injected to produce a distinct fall of 

 blood pressure, whilst those of the pituitary body pro- 

 duce a marked rise. 



Does it not seem distinctly probable, therefore, that 

 every tissue in the body to some extent affects every 

 other tissue? Each may have its own specific products 

 of metabolism, and perhaps specific internal secre- 

 tions, which, passing into the general circulation, may 

 in turn stimulate or depress, or otherwise affect, 

 every other tissue in the body. Whenever a changed 

 environment acts upon the organism, therefore, it to 

 some extent affects the normal excretions and secre- 

 tions of some or all of the various tissues, and these 

 react not only on the tissues themselves, but also to a 







