XLV INTRODUCTION. 



simply a manifestation of a general constitutional disturbance. The whole brunt 

 of the attack, it is true, often falls upon one particular part, but if that part were 

 not there it would assuredly display itself in some other region. 



One of the greatest advances that practical medicine has made during the last 

 quarter of a century is the recognition of the fact that you cannot treat a local 

 disease without reference to the constitution of the patient. For example, in 

 bronchitis in a child both the prognosis and treatment would be greatly modified by 

 a knowledge of the fact that the little one came of a consumptive stock, or was the 

 subject of rickets. Again, in Bright's disease our opinion would be influenced if we 

 learnt that the patient had suffered from gout or syphilis. So in regard to many 

 brain diseases, for the successful treatment of which a knowledge of the constitution 

 is essential. 



Of constitutional diseases we recognise the fact that some make their entrance 

 into the system from without, as, for example, scarlet fever, measles, and chicken-pox, 

 whilst others cannot be traced to external poisonous influences. A man has an 

 attack of rheumatism or gout, but we never suppose that he has caught it of any 

 one, but say that it is something peculiar to his constitution, either hereditary or 

 acquired. The so-called local disease we classify according to the organ primarily at 

 fault. Thus we speak of diseases of the nervous system, of diseases of circulation, 

 respiration, and so on. Then these may be further subdivided ; for example, in 

 nervous diseases we speak of affections of the brain, of the spinal cord, and of the 

 nerves. 



We now pass on to the consideration of the " etiology " or causation of disease. 

 Sometimes it is quite easy to discover the cause of a malady, or of any particular- 

 attack, and sometimes it is very difficult and well-nigh impossible. Let us take a 

 very simple case, where the cause of the disease is readily recognisable. A child is 

 brought into a room where some one is ill with scarlet fever, and after a certain 

 interval the disease makes its appearance and runs its usual course. Here we have 

 no hesitation in saying that the cause of the fever was contagion the child caught 

 it. But it must be remembered that if half a dozen children had been taken into 

 the sick-room, they in all probability would not all have caught it, some would have 

 escaped, though they had never had it before, and were equally exposed to the infec- 

 tion. This is quite in accordance with our general experience, for we know that 

 there are certain people or certain constitutions apparently unsusceptible to certain 

 poisons. There are people who have been vaccinated over and over again, but who 

 " never take," however often it may be tried, or however varied may be the source 

 from which the lymph is obtained. Then, again, physicians know that among the 

 students in the fever-wards the slightest exposure will in certain instances ensure 

 an attack, whilst others, even more diligent in their attendance on the sick, escape 

 altogether. There is even in some families a certain proclivity to fever, of which 

 probably most of us have met with examples, whilst others escape from even the 

 closest exposure to concentrated contagion. How do we account for this 1 What 

 is the explanation of it 1 We don't know. All we can say is that certain people 

 are " predisposed " to certain kinds of disease, whilst others are indisposed, or not 

 predisposed. When a person has already suffered from a fever, we know that he- 



