HOW TYPHOID FEVER IS CONVEYED. 465 



lescence from scarlet fever in fixing the particles of peeling skin, which 

 are a source of much danger. They are dangerous because they con- 

 tain the germs which have been produced in them. What we see hap- 

 pen in the larger particles of skin happens also in many of the much 

 smaller particles of contagion. 



By the adoption of these various measures, by rigorously isolating 

 the sufferer, and by having the room well ventilated, much, very much 

 may be done to check the spread of contagious fevers. The matter 

 of which organisms are composed is one of the most perishable things 

 in nature. Contagion is no exception to the rule. By exposure to the 

 air much of it is destroyed ; hence such exposure is one of the best of 

 all disinfectants. 



Sanitary science has done much to show us how some of the diseases 

 with which we are now dealing might be extinguished, and how all of 

 them might have their prevalence greatly diminished. It rests with 

 those who have such ailments in their houses to carry into effect the 

 measures calculated to destroy and get rid of the poison, before it has 

 had time or opportunity to be a source of danger to those around. 

 But the adoption of proper measures presupposes a knowledge of the 

 nature of the poison with which we have to deal, and of the manner 

 in which it passes off from the system. In not one is this knowledge 

 more necessary than in typhoid fever ; in not one are the measures 

 which such knowledge dictates more easily applied, or more likely to 

 be effective. But, to regard typhoid fever as contagious in the sense 

 that small-pox and typhus fever are so, is to divert attention from the 

 true source of danger, to lead to the adoption of measures which are 

 uncalled for, to the neglect of those which are urgently required ; is 

 to cause unnecessary concern to the sufferer and his friends, and to 

 deprive him and them of the mutual comfort and solace which a little 

 daily intercourse affords. The peculiarities of the illness may be such 

 as to make it right to exclude the friends ; but isolation is not requi- 

 site for the same reason that it is so in typhus. 



One more point. The receiver as well as the giver of the poison 

 has something to do with the determination of its action. Not every 

 person into whose system a germ passes necessarily suffers from its 

 action. A man who has had small-j^ox, for instance, is no longer sus- 

 ceptible to the action of its poison — and why ? Not because the poison 

 can not get into his system, for we can make sure of that by inocu- 

 lating him with it, but because, during the first attack, the nidus, the 

 special material necessary to its propagation, was exhausted, and has 

 not been reproduced. This immunity from a second attack is a gen- 

 eral characteristic of the eruptive fevers ; individual exceptions there 

 are, but the rule is that one attack confers immunity from a second. 



A germ does not act unless it reaches its nidus ; it may enter the 

 system, make the round of the circulation, and again pass out without 

 ever coming in contact with its nidus, and therefore without doing harm. 



VOL. XVI. — 30 



