212 



performing the functions which the brain was designed to 

 discharge. They may multiply fast^ and take up more 

 nourishment than the brain cells, had they been formed, 

 wouhl have appropriated, but the brain with its marvellously 

 complex intricate structure which involves gradually pro- 

 gressive changes, steadily proceeding during a length of 

 time, will never be produced ; and under no circumstances 

 conceivable could any of these masses, or any of their 

 descendants, develop one perfect brain cell. If progress 

 towards the mature state be stopped at any point, the perfect 

 state of development can never be reached, and the organism 

 if developed must be imperfect. The development of other 

 complex organs may have proceeded with perfect regularity, 

 but the organism must ever remain incomplete in structure, 

 and incapable of performing all the functions it might have 

 discharged. 



But although developmental power may be lost for ever, 

 power of a different kind may be acquired pari passu during 

 the rapid multiplication of bioplasm. Progressive advance 

 in the capacity to form lasting structures and elaborate organs 

 is characterised by the comparatively slow but regular and 

 orderly growth and multiplication of bioplasm. Rapid mul- 

 tiplication of the bioplasm, on the other hand, involves 

 degradation in formative power, which is at length entirely 

 lost, never to be reacquired. 



Degradation in power is commonly associated with 

 increased rate of growth, increased faculty of resisting adverse 

 conditions, and, in some cases, such is the vitality of the 

 living matter that it takes up the nourishment which should 

 be approjiriated by healthy parts, and these are at length 

 starved and deteriorate or are completed destroyed. The 

 actively living degraded bioplasm may be capable of retain- 

 ing its vitality although removed altogether and for some 

 time from the living body, and, remarkable as it seems, it may 

 grow and at length destroy other living organisms to which 

 it gains access. 



The poisonous " virus " of many contagious diseases is, 

 I shall endeavour to show, living matter or bioplasm, which 

 has been derived by direct descent from the bioplasm of a 

 healthy organism, and I propose in this paper to give a 

 sketch of some of the most important facts which have led 

 me to adopt this vieAV. The inquiry is of great interest, not 

 only because it affects the question of the nature of the 

 material concerned in the propagation of contagious diseases, 

 but it will be found to bear upon matters of the greatest 

 practical importance, such as the means of preventing the 



