BLOOD DISEASES. 145 



these life forms could be gathered and continuously distributed 

 in the tissues artificially. 



In many of Straus' experiments, and others of this class 

 referred to above, agents were introduced that evidently 

 paralyzed the tissues, and as pus formation is a vital act, it 

 was necessarily prevented. Every such element must be 

 rigorously excluded from our experimentation before the 

 results can be depended upon as conclusive. 



BLOOD DISEASES. 



The production of disease, however, is not limited to in- 

 flammation and pus formation. Many of the diseases now 

 supposed to be parasitic in their causation are not essentially 

 inflammatory, but are known as systemic or blood diseases. 

 This class of diseases are not caused by any simple irritant, but 

 by some toxic element developed by the organisms. As to 

 what this toxic element may be we have only conjecture, but 

 after what we have just said in reviewing the waste products 

 of the various life forms, this conjecture is a close approach 

 to knowledge. The elements of the compounds are pretty 

 certain to be written C H N O, in varying equivalents. It is 

 possible that the N may be left out of some, or that the O 

 may be left out of others. But this is not very probable. 

 We know enough of the alkaloids, to know that they may 

 become a potent cause of disease, if developed continuously 

 in the blood or tissues. 



It may be said that we know of no alkaloids that will 

 produce the effects shown in the diseases that we see 

 around us. This is very true. A few years ago we knew 

 of no alkaloid that would produce the effect of woorara, or 

 quinine, or atropine, or strychnia; and when we have dis- 

 covered others, and have learned their effects, they will be as 

 easily understood as those now known to us. That systemic 

 disease may result in this way, is not only possible, but it 



