THE CAUSATION OF DISEASE. XV 



is " protected " from a second attack, or no longer predisposed to take it again, but 

 this absence of predisposition is undoubtedly present in many instances where there 

 has been no previous attack. These constitutional peculiarities, if we may so term 

 them, are not unknown in other departments of nature. On some sunny slope, well 

 drained, and well exposed to wind and rain, uniformly cultivated and manured, 

 Bown with the same seed on the same day and by the same hands, we find inequality 

 of produce ; the fair expanse is marred by some one spot where the crop is 

 dwarfed, insufficient, or altogether absent. We cannot account for this, for it may 

 occur at some spot where on former years there has been, from the same materials 

 of labour and seed an abundant result, nay more, where next year or a year or two 

 later there may be, under identical circumstances, an exceptionally tine crop. From 

 this it would appear that there must be something more than a prepared soil and 

 healthy seed, something more than an intense contagion and direct exposure to its 

 influence, and this something we call " susceptibility or predisposition." 



In many instances it is very difficult to say what the cause of a disease has been. 

 For example, a child is attacked with St. Vitus's dance ; there has been no previous- 

 illness, we cannot learn that the child has been frightened, and we are absolutely in. 

 the dark as to why those peculiar symptoms should have made their appearance. 



Then again the same cause is in different people often followed by very different 

 results. For example, half a dozen people partake of an indigestible meal, one of 

 them is none the worse for it, a second suffers from indigestion, a third has a fit, a. 

 fourth gets an attack of gout, a fifth has an attack of asthma, whilst the sixth has 

 diarrhoea. Here the exciting cause, the indigestible meal, is the same in all, but the 

 results are widely different, and we say that this depends upon the constitution. 

 ' We recognise the fact that certain people are liable to suffer from certain diseases, in 

 other words, they are subject to them, and anything that throws them off their 

 equilibrium is likely to induce an attack of the disease to which they are " pre- 

 disposed." 



We must now consider briefly what are the predisposing causes of disease. 

 Some people are hereditarily predisposed to certain complaints. The son of a gouty 

 parent is very likely to become gouty unless he specially guards against his 

 predisposition by strictly abstemious habits. Cancer is more or less hereditary, and so 

 is consumption. That consumption may be transmitted from parent to child is one 

 of the best-established facts in medicine. The extreme frequency of consumption in. 

 some circumscribed country districts is, in part at least, explicable by the frequency 

 of intermarriage amongst persons living in such districts ; and conversely, the 

 exemption of particular circumscribed districts from this disease is in part due to- 

 the same cause. In the one case, from some special circumstances, consumption has 

 been introduced into the district, and then spread in it from frequent intermarrying. 

 In the other case, the freedom of the district from the disease at any given time is 

 the cause of its continued freedom. Intermarriage of the inhabitants, the disease 

 being present, spreads it far and wide, intermarriage of the inhabitants, the disease 

 being absent, prevents its introduction. This circumstance has not been sufficiently 

 recognised in estimating the causes of the relative frequency of consumption in 

 different localities. 



