Blood and Blood Vessels. 225 



All these forms occur in the embryo, apparently nor- 

 mally; some of them are certainly transition forms. They 

 also bear a resemblance to the red cells of lower verte- 

 brates. Are these not clear cases of reversion to an earlier 

 condition, both embryonic and ancestral ? Even that form 

 of anaemia in which the cells are fairly normal, excepting 

 a deficiency in haemoglobin, points to the lower vertebrate 

 and invertebrate blood, which is, relatively to the higher 

 groups of animals, poor in haemoglobin. 



Inflammation itself, both as regards the vascular system 

 and the tissues, becomes clearer from the standpoint of 

 evolution. The increased amseboid activity of the leuco- 

 cytes, the alterations in the latter and the vessel walls per- 

 mitting of the ready " wandering " of the colorless blood- 

 cells, point to a condition of things common in lower verte- 

 brates. Inflammation is clearly a reversion. 



Reference might be made to the resemblance between 

 the condition of things in the young mammal — in which, 

 after birth the usual changes that fit it to its altered en- 

 vironment do not take place — and the permanent state of 

 the heart and vessels in lower vertebrates, as reptiles. 

 However, the illustrations employed may suffice to show 

 that evolution does concern the physiologist, the patholo- 

 gist, and the physician ; and, did time permit, I think I 

 could demonstrate that such views may be made to have a 

 bearing on the treatment of disease by the most enlightened 

 methods. The subject has been dealt with further in its 

 relations to medicine elsewhere. 1 



I shall not pursue this line of thought further at present, 

 but leave you to judge for yourselves whether the time has 

 come when students and practitioners should be provided 

 with text-books of physiology in which attention is paid to 

 general biology, comparative embryology, and evolution, 

 with a view of giving a wider and truer grasp of the 

 functions of those organisms with which the great art of 

 medicine is concerned. 



1 Physiological and Pathological Reversion. Canada Med. and 

 Surg. Journal, April, 1888. 



