THE CAUSATION OF DISEASE. 1 93 



Thus, the E of the fish differs from that of the mammal, 

 which again is different from that of the bird. Nor is this 

 all. The E of each species of fish, bird, and mammal — . 

 indeed, of every species of animal — is different from that of 

 any other ; and it is the special purpose of instinct and 

 reason to secure the proper E for each. If the ant had the 

 instinct of the worm, or the latter that of the lizard, neither 

 could provide itself with the proper E, and both would 

 inevitably perish. But matters are so happily arranged that 

 each animal has the inborn power of regulating its E more or 

 less correctly. 



The E of man is infinitely complex. As the division 

 of labour proceeds in the social organism, the number of 

 different kinds of E increases, and thus every man following a 

 different calling is surrounded by a different E. There is not, 

 therefore, one limited and more or less stereotyped E for each 

 and every member of the human species, such as obtains in 

 the case of any one species of the dumb animals. 



Now, so far as the en viro- regulating apparatus is concerned, 

 man and the brutes stand out in bold contrast, in that reason 

 is the chief means of the one, instinct of the other. I will not 

 here set forth in critical detail the distinctions between instinct 

 and reason. It is sufficient to observe, that the one impels by an 

 inborn power, which ties down the individual to act mechani- 

 cally, so to speak, on a narrow and stereotyped plan ; while 

 the other is a more or less complex mental process, in which 

 the inborn guiding voice finds but little place. The subtle 

 psychological distinctions between instinct and reason need 

 not, however, detain us. That there is a distinction is clear, 

 and for pathological purposes, if for no other, it is very 

 necessary to recognize it. And why ? Because the one regu- 

 lates the E perfectly, while the other is a defective regulator ; 

 the one places the individual amid the E to which he is 

 best adapted, while the other frequently fails to do so. And 

 inasmuch as disease essentially originates in improper E, this 

 deficiency in the enviro -regulating system becomes a fertile 

 source of disease. 



Instinct is the most perfect possible guide. Few, I imagine, 

 will deny this proposition ; but lest any should, we have 



