420 COLLECTED STUDIES IN IMMUNITY 



the tissues with oxygen, reaction of the tissues (nephritis in chromium 

 poisoning), conditions of alkalinity, peculiarities of elimination, etc , 

 affect the result in any given case cannot now be discussed. We 

 find exactly the same conditions to hold with bacterial poisons. 

 Tetanus poison, for example, as is shown by the experiments of 

 Ddnitz, Roux, and others, is monotropic in highly susceptible animals, 

 whereas in other animals, rabbits, pigeons, etc., the tetanus-binding 

 groups are present not only in the brain but also in a number of other 

 organs of less biological importance. This explains why, for instance, 

 in guinea-pigs the lethal dose is the same whether the poison is in- 

 jected subcutaneously or intracerebrally, whereas in the pigeon, 

 and to a certain extent also in the rabbit, much larger doses are 

 required for subcutaneous poisoning. Under these circumstances 

 part of the poison is laid hold of by the body parenchyma and thus 

 deflected from the endangered organs. 



We may perhaps regard it as a matter of course, that these laws 

 of mutual deflection play an important role in all polytropic sub- 

 stances, and that we shall gain a real insight into the action of drugs 

 only if we regard this factor sufficiently. If, for instance, as is so often 

 the case, a poison is both neurotropic and lipotropic, if the same 

 amount of poison per kilo body weight is injected into a lean animal 

 as into a very fat one, it is clear that the share of poison which falls 

 upon the brain in the former case is much greater than in the latter. 



IV. 



We now take up the question as to how this varied distribution 

 occurs. As a rule the poisons reach the tissues through the circu- 

 lation, and we shall therefore first study the influence of the vascular 

 system on this distribution. A moment's consideration, however, 

 shows that although the circulation may be the prerequisite, it can 

 in no way be the cause of the varied distribution discussed above. 

 According to the views held by the majority of investigators and 

 also by me this localization in certain organs depends in every in- 

 stance on causes within the tissues and not on the vascular distri- 

 bution. For example, if in a case of jaundice we find that the brain 

 shows not a trace of bilirubin coloration, while many other tissues, 

 such as kidney, liver, etc., are saturated with bile pigment, this, in 

 my opinion, is due to the chemistry of the brain substance. The 

 brain lacks all such substances which attract bilirubin, that is to 



