4/6 ]Nflui-:nck of ilimati-: tn\ ammal disease. 



This question of envirf)iiment we may examine in a little 

 more detail, as it is connected with the later part of our subject. 

 If we do so, we soon meet not only with the importance of the 

 climatic factors of sunshine and rain actin^^ as the direct sources 

 of supply of the warmth and moisture necessary in the above 

 connection, but also with the importance of other factors which, 

 in the title of this paper have been referred to as tellurical. 

 Under this latter term we recognise all those ])eculiarities in 

 regard to character and nature of soil, vegetation, geological 

 formation, minor surface relief and water supj^ly of any given 

 locality, and the importance of these in regulating the retention 

 and distribution of the heat and moisture supplied by the climatic 

 elements is obvious. In the following paper, however, the attenn)t 

 is made to make an additional importance of these conditions 

 more evident in the present connection, and this by jjointing 

 out how through soil or vegetation, or collections of water in the 

 form of rivers, streams, pools, marshes, vleis, pans, etc., or a 

 combination of these, they may provide habitats suitable to the 

 existence and development of either a transmitting or interme- 

 diate host of a disease-causing organism, or a disease-causing 

 organism itself. 



These remarks bring us nearer to our main subject, and it 

 is unfortunate that time and s])ace do not allow of these general 

 considerations being further ])ursue(l. If they did, we might 

 have dealt with the interesting ])art that civilised man has played 

 in the distribution of trojjical and sul)tro])ical diseases through 

 his habits, and the changes he has produced in the tellurical con- 

 ditions of the countries where they occur, 1)v the methods he 

 uses in o])ening u]) and developing these newer lands and fur- 

 thering his agricultural and pastoral pursuits within them. We 

 might also have pointed out how tiie sjiecial i:)roblems which 

 these diseases otter have atttracted a certain bodv of workers to 

 study them, and how the results of their researches have come 

 not only to give the terms tro]>ical and subtropical diseases the 

 .significance they [possess in medicine at the present day, but 

 also to furnish man with measures for combatting these diseases. 

 thus giving him further scope in influencing their distribution. 



These considerations, liov.^ever, would furnish materials for 

 several papers in themselves, and hence we must leave them in 

 proceeding to the more detailed examination of our subject. In 

 doing this latter the writer may mention that he does not intend 

 to enter into a description of the climatic and tellurical condi- 

 tions existing in South Africa — conditions with which the reader 

 is no doubt well ac(|uainte(l — but. taking them as they are. in- 

 tends to attempt to exjjlain their influence on the spread of 

 disease, illustrating this in taking as exam])les animal diseases 

 commonly occuring in this sub-continent. For this purpose a 

 convenient grouping of the tyi^es of diseases dealt with will be 

 necessary, and perhaps the most suitable procedure is to group 

 them under the four headings of — 



