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species well known to all bacteriologists as particularly 

 insusceptible to the disease. Of course it is needless 

 to say that these same authorities are quite sure that 

 tuberculosis is hereditar}^ forgetting (if indeed some 

 of them ever knew the fact) that what is caused by 

 the adventitious agency of a microbe — a foreign 

 invader — during post-natal life can scarce!}^ have been 

 present at the time of the formulation of the original 

 germ-plasm, often many years previously. Leaving 

 this disease for the present however in the hands of 

 our friends, we will now proceed to the discussion of 

 Septicaemia ; but for the better understanding of the 

 subject we will first take a fleeting and cursory glance 

 at some of the various forms of parasitic life in a 

 general way, doing so in the simplest manner possible 

 in the consideration of so intricate a subject. 



Parasites admit of — indeed they demand — the 

 most varied classification. Firstly the}^ may them- 

 selves be either animal or vegetable : secondly both 

 forms may attack either animals or vegeta])les. With 

 those that attack only the latter we have no concern, 

 and will therefore confine ourselves to the consider- 

 ation of those that pre}^ upon either living animal 

 tissues, or dead animal and vegetable matter, or both. 



Some attack only the outside of the body, others 

 the internal parts : some attach themselves to many 

 kinds of animal, others to only a few species : some 

 are parasitic during the whole cycle of their existence, 

 others during onh^ a portion of it. 



The chief animal parasites that infest birds are 

 certain species of wingless insects (lice), of arachnida 

 (mites), and entozoa (worms), all of which possess 

 analogues to be found on and in the human body, but 

 which unlike them have as 3'et received only very 

 scant attention at the hands of scientific observers. 

 It is true that a few of them have been identified 

 and relegated to their proper position in the animal 



