338 THE CAUSATION OF DISEASE. 



impossible to arrange diseases as fixed and unalterable types, 

 owing to the fact that the several specific mal-E's are not fixed 

 and unalterable. In some few cases it would be possible to get 

 exactly the same mal-E, as in the case of the ordinary chemical 

 poisons ; for instance, if we suppose two individuals exactly 

 alike structurally to take exactly the same dose of the same 

 poison, the resulting disorder will in each case be exactly the 

 same. But, as a matter of fact, such coincidences as regards E very 

 rarely occur, and if in so simple a case the mal-E is not stable, 

 how much more unstable shall we find it in other cases ? Take, 

 for example,- the gout-producing E. In. this case the E extends 

 over a long period of years, and, in consequence, it is utterly 

 impossible for it to be exactly alike for any two individuals. 

 This will be readily granted when the highly complicated 

 nature of the external-E is borne in mind. As another 

 instance, we may cite a specific -fever-engendering E. Inas- 

 much as the mal-E is in this case a poison, it might be 

 thought that therefore its inter-action with S would be identi- 

 cal in all individuals coming under its influence ; but such is 

 not the case, for the poison being the product of living- 

 organisms, and these being liable to vary, the poison is liable 

 to vary also. Hence it is that no two epidemics are exactly 

 the same, and that they are apt to die out, disappearing from 

 the face of the earth, while new ones come continually into 

 being. So wide, indeed, are the deviations from the classical 

 types of the so-called " specific fevers," and so numerous the 

 unnamed and unrecognized forms of allied disorders, that it 

 becomes at once evident how very imperfect their classification 

 must be, and that a very elastic meaning to any terms, we 

 employ to denote these types must be allowed. This subject 

 has been so ably discussed by Dr. W. J. Collins * and Mr. 

 Millican,f that it is unnecessary to pursue it further. 



The same line of argument applies to all forms of mal-E. 

 They are essentially variable, and such being the case, the 

 diseases which they cause must be variable also, even though 

 the S be the same ; and inasmuch as the S of all individuals 



* " Specificity in Evolution," by W. J. Collins, M.D., &c. This is a valuable 

 paper, and deserves careful study. 



(• "The Evolution of Morbid Germs," by Kenneth W. Millican, M.B. 



