AND ITS KELATIONS TO THE LIVING ORGANISM. 289 



the poison is continually arising ; and its operation ceases, therefore, as soon 

 as it is entirely eliminated from the system. But there is this peculiarity in 

 the action of many of the poisons in question, that they have the power of 

 multiplying themselves within the body; thus, for example, when small- 

 pox has been communicated by the inoculation of an excessively minute 

 portion of the virus, hundreds or thousands of pustules are generated, each 

 of them charged with a poison equally potent Avith that from which they 

 originated. It is to this multiplication, that the extension of zymotic dis- 

 eases, by communication between individuals affected with them and healthy 

 subjects, is chiefly due ; and the question of the "contagion" or "non-con- 

 tagion" of any particular disease of this class, is, therefore, essentially that 

 of the multiplication or non-multiplication of the poison in the human 

 body. This multiplication of certain zymotic poisons is a yet stronger point 

 of analogy to the action of " ferments," than that which is afforded by the 

 violence of the changes they induce when compared with the amount in 

 operation. Some of these poisons are of such potency, that, in however 

 minute a quantity they are introduced, they will change the whole mass of 

 the blood in a few minutes, and will act indiscriminately on all individuals 

 alike; this is the case, for example, with the venom of serpents. On the 

 other hand, there are many (as already remarked) which seem to require 

 the presence of some special fermentable matter in the blood ( 223). And 

 between these might probably be established a regular gradation from 

 those most "pernicious" forms of malarious poison, which derive their po- 

 tency from the intensity of vegetable decomposition under the influence of 

 a high temperature; or those "malignant" types of typhoid poison, which 

 owe their special intensity to animal putrescence engendered by filth and 

 overcrowding ; both of these attacking a very large proportion of those who 

 are exposed to them to those milder forms of zymotic poisons, which, 

 though derived from the same sources with the preceding, act with so much 

 less of uniformity upon different individuals, that we can scarcely fail to 

 recognize as a " predisposing cause," or rather as a necessary concurrent 

 condition, the presence of some readily-decomposable matter in the blood. 

 The long-continued action of these poisons, in their milder forms, seems 

 itself capable of inducing this condition; thus, a healthy person who settles 

 in an aguish country, may remain free from intermittent fever for a consid- 

 erable time, but his health gradually deteriorates, and at last he becomes 

 the subject of the disease, which would have much earlier attacked him if 

 his blood had been brought into the " fermentable " state by irregularity 

 of diet, over-exertion, etc. ; and the same may be observed in the case of 

 those long exposed to the poison of typhoid or other fevers, which espe- 

 cially locates itself in animal miasmata, if it be not actually engendered by 

 them. 



228. In some of the diseases of this class, the change in the qualities of 

 the Blood produced by the introduction of the poison is such as to g've it a 

 morbid action on certain organs or tissues only; their phenomena in this 

 respect corresponding with those of ordinary poisons, and of the toxic dis- 

 eases previously noticed. Such may be said of vaccinia, gonorrhoea, pri- 

 mary syphilis, etc., in which the general functions of the body seem to be 

 disturbed chiefly or solely through the local disorder. It may happen that, 

 even where a specific poison is present in the blood, it may not be potent 

 enough to manifest itself in any disordered action, either general or local, 

 until the depressed state of the nutrition of some part or organ renders it 

 more susceptible of a further perversion ; thus it is very common for the 

 first development of Cancer to follow upon some local injury ; and where 

 constitutional Syphilis may be presumed to exist, it often seems to lie dor- 



