266 ROYAL SOCIETY OF CANADA 



were a variety of protective mechanisms potentially present, any one 

 or more of which may on occasion be called into play. That these 

 mechanisms are not altogether specific is shown by the fact that to some 

 extent they can be manifested by normal tissues and body fluids and 

 seem to be a fundamental property of cell-protoplasm. While it is 

 true that certain of them can be increased in potency by the injection 

 of bacterial toxins and then probably become specific, yet these pro- 

 tective substances can be elaborated in other ways. The curative action 

 of the ferment of yeast or saccharomyces in cases of infection with a 

 germ of a different class, the staphylococcus, is a case in point. Some 

 other interesting facts may also be referred to in this connection. More 

 than forty years ago a distinguished member and former president of 

 this Eoyal Society, Sir James Grant, M.D., made a striking series of 

 observations on the action of the lymph of cow-pox (vaccine) in the 

 case of certain skin diseases {London Medical Times and Gazette, 

 March 14th, 18fio). Affections, such as psoriasis palmoris, tinea 

 nummularis, psoriasis laprœformis, and even syphilis, which had resisted 

 for years the ordinary measures, yielded in a comparatively short time 

 to the action of vaccination of the Jennerian type. We are not sure, 

 of course, of the -etiological factors at work in the diseases mentioned, 

 but, if not microbic, they are at least due to blood dyscrasiœ and the 

 products of the metabolism of the organism of cow-pox, whatever it 

 may be, affected some alteration in the system which resulted in cure. 

 Again, occasional instances are met with where the toxin of one germ 

 is antagonistic to the growth of another. At least, this can be sho-wTi 

 in vitro. The products of growth of certain bacteria, such as the 

 B. Prodigiosus and the micrococcus of erysipelas, have been found to 

 be detrimental to cell growth and metabolism, as witness the beneficial 

 effect that Coley's method of treatment has in some cases of malignant 

 disease. Facts such as these still want explanation, but farther study 

 along these lines may eventually result in the discovery of laws which 

 will be valuable in the therapeutics of infectious disease. All, how- 

 ever, goes to show that the laws governing immunity are of the widest 

 scope, and that the process is probably in the main to be explained on 

 chemical principles, though the vital properties of the cells and tissues 

 are by no means to be neglected. 



