224 Canadian Record of Science. 



enough, its great doctrines have thus far made very little 

 impression on physiology, especially the teaching of the 

 subject ; and my own text-book is the first and only one in 

 which an attempt has been made to light up the student's 

 path with this theory; and you will be glad to hear that 

 this effort has been rewarded by increased interest in phy- 

 siology on the part of my own classes during the four years 

 of trial of the new methods of presenting the subject. 



But if this is good for students that are undergraduates, 

 may it not also prove helpful to practitioners to regard 

 disease in the light of evolution ? 



Physicians have given but little attention to the subject. 

 To this statement, however, there are at least two notable 

 exceptions : the late brilliant Milner Fothergill, and that 

 profound thinker, of whom we are so proud the world over, 

 Hughlings Jackson. 



Turning to the vascular system in the wider sense (the 

 blood and blood-vessels), by the help of evolution and em- 

 bryology not only are many anomalies of vessels under- 

 stood, but also of the blood itself. 



Does not a case of extreme multiplication of leucocytes 

 in the blood indicate a condition at once embryonic and 

 ancestral ? In other words, is not this an example of 

 physiological or pathological reversion ? In the early em- 

 bryo, leucocytes are very abundant everywhere, and in 

 invertebrates, almost without exception, they or their equi- 

 valents, are alone found, while in the lower vertebrates they 

 are both numerous and of very much more pronounced 

 amoeboid character than in the higher. Is not this ten- 

 dency, then, on the part of the higher mammals and man, 

 under certain circumstances, to an excess of leucocytes in 

 the blood better understood than without the explanation 

 of evolution ? Why this particular form of derangement, 

 and not some other, if higher forms are not related by 

 descent to the lower ? 



Again, in the various forms of anaemia we find red cells 

 that are nucleated, cells smaller or larger than normal, 

 distorted cells, corpuscles resembling the genetic marrow- 

 cells, etc. 



