October 27, 1893.] 



SCIENCE. 



231 



INMUNITY AND CUBE IN THE INFECTIOUS DIS- 

 EASES. 



BY VICTOR U. VAUGHAN. 



Immunity may be natural or acquired. Natural immun- 

 ity may be peculiar to the species or race, or to the in- 

 dividual. An example of natural immunity is that of the 

 domestic fowl to aathras. This aaimil, even at the time 

 of coming from the shell, is immune to even the most vir- 

 ulent cultures of the bacillus anthracis. It is true that 

 the chick may be made susceptible to anthrax, but this is 

 an artificially induced suscei^tibility. Immunity is natural 

 to this bird at every period of its life. 



The natural inmunity which is peculiar to the indivi- 

 dual usually comes with adult life. The young are sus- 

 ceptible to a given disease, but adults of the same sjJecies 

 lost this susceptibility and become immune. The young 

 rat is susceptible to anthrax, while the adult is naturally 

 immune, but can be rendered susceptible by exhaustive 

 exercise. The child is highly susceptible to scarlet fever 

 and diphtheria, while the adult, though not wholly im- 

 mune to these diseases, loses very much in susceptibility 

 and is likely to become affected only when greatly re- 

 duced in vitality, or after prolongad and aggravated ex- 

 posure to poison. Ths evolution of the condition of im- 

 munity in these cases is due to the natural development 

 of the fanctional activity of certain cells of the body. A 

 child and an adult are exposed to the bacillus of diphth- 

 eria from the same source. The former becomes affected, 

 the latter does not- The germ is the same, but in the de- 

 velopment that converts the child into the adult, the re- 

 sistence with which the germ must contend has been 

 strengthened. Artificial immunity may be induced by 

 either of the following methods : 



1. By an attack of the disease ending in recovery. 

 Until the discovery of Jenner, this was the only known 

 cause of immunity, and even at jiresent it is supposed to 

 be, as far as man is concerned, the most potent cause. It 

 is true, I believe, that the more grave and virulent the 

 disease may be, the greater and more persistent is the 

 immunity that follows. I mention this in order to call 

 attention to the fact that there is a quantitive relation be- 

 tween cause and effect in the production of immunity. 

 In this method of inducing immunity, the substance of 

 the germ itself is introduced into the body. This method 

 found a practical application in inoculstion for the pre- 

 vention of small pox. 



2. By vaccination with a modified and less virulent 

 form of the infection, or by the introduction of at first a 

 very small number of the virulent germs and successive 

 inoculations with larger numbers. The successful inocu- 

 lations against chicken cholera and anthrax made by Pas- 

 teur consist in vaccination with a modified germ, and the 

 valuabb investigations of Emmerich and his students in 

 immunizing certain animals to swine erysipelas have 

 demonstrated the results that may be obtained by employ- 

 ing the virulent germ, first in small numbers, and then 

 gradually increasing the doses. Again, it may be obser- 

 ved that the germs themselves are introduced into the 

 body, and again it is also true that the more potent the 

 cause, the greater and more persistent the effect. 



3. By one or more treatments with sterilized cultures 

 of the germs. Inmunity against the gems of typhoid fever, 

 chojera, diptheria, tetanus, hog cholera, and several other 

 diseases, has been secured bj' one or more treatments 

 witn sterilized cultures of these germs. In answering" the 

 question, which eonstituent of sterilized cultures gives 

 inmunity, we must bear in mind the following facts. 



a. Marked artificial inmunity to the infectious diseases 

 has not been obtained except by the introduction into the 



animal of the gem substance, either enclosed in the cell 

 wall or in solution. ^ 



b. Sterilized cultures contain the germ substance in 

 one or both of these forms. 



c. The same immunizing substance exists in the bodies 

 of bacteria grown on solid media and killed by the action 

 of choloroform. 



d. The same immunizing effects, varying, however, in 

 degree, are obtained with the bodies of dead bacteria 

 morphologically intact or in solution, with living bacteria _ 

 modified and reduced in virulence, and with very small 

 numbers of the virulent germ. 



With these demonstrated facts before us, I am ready to 

 believe that the immunizing substance is a constituent of 

 tne bacterial cell itself, and as each kind of germ has its 

 own peculiar poison (which in small doses confers immun- 

 ity), this poiaoa cannot come from the cell |wall; nor is it 

 really a split product of tne germ's action, but it is the 

 essentially characteristic part of the cell— that part wnicn 

 gives to tne germ its distinctive properties. I believe that 

 it is the nuclein. 



The three methods of inducing immunity which W9 

 have mentioned reduce themselves to one and the same 

 principle, i. e. the introduction of germ nuclein into the 

 body. 



The immunity that results from an attack of the disease 

 is caused by the introduction of germs living and more or 

 less virulent. That which comes from vaccination is due 

 to the introduction of germs living but modified and re- 

 duced in virulence, or administered in small quanity; that 

 which is obtained by one or more treatments with steril- 

 ized cultures is secured by the introduction of germ nuc- 

 lein so modified that it is no longer capable of reproduc- 

 ing itself. 



4. By treating a susceptible animal with the blood 

 serum of an immune animal. 



Strange as it may seem, the principle upon which 

 immunity is secured when the blood serum of an immu- 

 nized animal is injected into a susceptible one is essen- 

 tially the same as that which holds good in the methods 

 already discussed. A horse is rendered inmune to 

 tetanus by previous treatment with the modified bacterial 

 proteid of that disease. j\s a result of these treatments, 

 a tetanus antitoxin is generated in some organ or organs 

 of the horse and circulates in its blood. When the blood 

 clots, this antitoxin is found in the serum, and if the s serum 

 be injected into a mouse in sufficient quanity, this animal 

 becomes for the time being immune to the tetanus poison, 

 provided that the poison is not introduced in quantities 

 so large that it will not be destroyed by the antitoxin 

 that has been brought over from the horse. The immunity 

 actually does nor belong to the mouse, it still belongs to 

 the horse. It is stolen property and will soon be lost. 

 The cells of the horse and not those of the mouse make 

 the antitoxin. The mouse for the time being becomes 

 physiologically a part of the horse, and it is by virtue of 

 this relationshiij that the former is for the time being 

 immune to tetanus. 



We have seen that in all cases the cause that brings 

 into existance the condition of immunity is a bacterial j)ro- 

 teid. Nnw, in order that this inciting cause may induce 

 the condition of immunity, it must act upon something. 

 Upon what organs of the body does it act? We have 

 many reasons for believing that the organs acted upon 

 are, the spleen, bone narrow, thyroid and thymus glands, 

 and possibly other grandular organs. Tizzoni and Cattani 

 have found that rabbits from which the spleen has been 

 removed cannot be immunized to tetauas. Suppiosing 

 that the above mentioned organs are concerned in the pro- 

 duction of immunity, in what way do they act? Do they 



