ON THE NATURE OF TOXINS 41 



which have the power of dissolving living cells or red blood- 

 corpuscles respectively from susceptible animals. 



In dealing with these substances we will consider firstly their 

 action, secondly their structure, and thirdly what has been estab- 

 lished concerning their chemical relationships with other sub- 

 stances. The last is comparatively unimportant. 



i. Action of Toxins. The results of the injection of a toxin 

 into a living and susceptible animal depend, in most instances, 

 on the dose injected. If, for instance, we inject a large amount of 

 the filtered broth in which the tetanus bacillus has been growing 

 for a month or so, and which in consequence contains tetanus 

 toxin, the animal (a guinea-pig, for example) will develop the 

 rigidities, spasmodic contractions of the muscles, etc., charac- 

 teristic of tetanus ; and these make their appearance after an 

 interval of some hours, during which period the animal shows 

 no symptoms whatever of the disease. Great stress was laid 

 at one time on the occurrence of this " latent period," since it was 

 thought to be peculiar to the bacterial toxins (and to the similar 

 substances of animal and vegetable origin), and to distinguish 

 them sharply from other poisons, alkaloids, etc. This is hardly 

 correct. It is true that in most cases of intoxication by bacterial 

 toxins there is a latent period, but in a few it is practically absent 

 The most interesting example is the " Nasik " vibrio, an organism 

 allied to that of cholera. This produces an exotoxin (though not 

 a very powerful one in the sense that it kills in small doses), 

 which proves fatal on intravenous injection into a rabbit after a 

 period of ten to thirty minutes, and symptoms are produced before 

 this. On the other hand, some of the alkaloids, and notably 

 colchicine, display a well-marked latent period. The phenomenon, 

 therefore, is not absolutely peculiar to, nor characteristic of, the 

 toxins ; but since it is so commonly displayed by them, it calls for 

 some investigation. Moreover, we must assume that part at 

 least of the incubation period of an infective disease is taken up 

 by the latent period of the bacterial toxin, a circumstance which 

 invests it with especial interest. Thus a horse which Madsen 



the corpuscles or of parts thereof; (2) the simple organic haemolysins, which 

 include the bacterial haemolysins dealt with above, the hsemolysins of vegetable 

 origin (such as ricin, etc.), and some of the haemolysins of animal origin ; 

 and (3) the compound haemolysins, all of animal origin, which will be dealt 

 with subsequently. These groups differ profoundly in their action, and must 

 be kept quite distinct. 



