THE OUTLOOK FOR HUMAN HEALTH 155 



disastrous scourge the human race has known, the discoveries 

 of Laveran and Ross have clearly demonstrated the etiology 

 of the disease and have pointed the way to its extirpation. 

 True it is that, owing to the existence in many places of 

 extensive swamps or of rice cultivation, the cost of the 

 necessary measures for the elimination of the Anopheles 

 mosquito seems at present prohibitive ; but the improvements 

 and inventions in the campaign against this malign insect 

 which will surely come in time will render practicable the 

 latter's disappearance in at least the most populous areas. 

 Final success may come slowly; it is unreasonable to expect 

 its advent swift as the lightning flash from a summer cloud. 

 By way of contrast to the complexity of this problem stands 

 the case of Malta fever. Here, once it had been ascertained 

 that goat's milk formed the medium of entry of the bacillus 

 into its human host, the prophylaxis was ridiculously easy; it 

 sufficed simply to abstain from goat's milk in order to eradicate 

 the disease. Sleeping sickness, that most gruesome and fantastic 

 of human ills, after decimating the population of Central Africa, 

 is in a fair way to be abolished. The trypanosome which 

 causes it takes, so it has been ascertained, as its secondary host 

 a tsetse fly which fortunately never wanders far from lakes or 

 rivers. Hence by moving the population to a specified distance 

 from such collections of water there is every hope that ere long 

 both human beings (and tsetse flies) will emancipate their bodies 

 from this parasite. Turning to temperate climes, all recognise 

 the enormous gain to human health and happiness wrought in 

 such cities as London or Glasgow, for instance, by measures of 

 sanitation — that is to say, by measures having for their object 

 the prophylaxis of parasitic diseases. In the fall of the death- 

 rate, in the absence nowadays of serious epidemics and in the 

 sinking into oblivion of diseases whose very names once struck 

 terror in the heart of the householder, we may discern the gleam 

 of the triumphant standards of science as they advance against 

 the hosts of disease. Even with diseases such as phthisis, which 

 are as yet far from being under control, science points out 

 certain simple precautions which, for those capable of following 

 them, render this dreaded disease as remote a peril as small-pox 

 to the properly vaccinated. No deeper chasm indeed divides 

 modern freedom of thought and independence of opinion from 

 the superstition of the middle ages than the immunity from 



