812 



SCIENCE 



[N. S. Vol. XXXII. No. 832 



insect acts chiefly as a carrier of the para- 

 site. 



The trypanosome which is of particular 

 interest on account of being the cause of 

 sleeping sickness is the Trypanosoma 

 Gambiense. It is disseminated by a species 

 of tsetse fly known as Glossina palpalis, 

 which somewhat resembles our common 

 house fly. According to Koch, the Glos- 

 sina subsists largely on the blood of croco- 

 diles, and he recommended that these 

 should be exterminated to reduce the num- 

 ber of insects. It has been shown by 

 others, however, that the tsetse fly disease 

 prevails in regions where there are no 

 crocodiles, and, vice versa, that it is not 

 met with in regions where these reptiles 

 are abundant. Probably in the course of 

 time some practical scheme will be devised 

 for exterminating these insects similar to 

 those in vogue in regions infected by the 

 mosquitoes which transmit malaria and 

 yellow fever. The task will be more diffi- 

 cult because the young of the tsetse fly 

 soon reach maturity, as they are born in 

 the larval state instead of being deposited 

 as eggs. 



One of the great difficulties in the 

 treatment of sleeping sickness has been 

 that in its early stages the symptoms are 

 so mild that the patients, chiefly ignorant 

 natives, do not resort to medical aid. 

 When seen by the physician, therefore, 

 the disease is generally far advanced, the 

 patient being emaciated, dull, apathetic, 

 dragging along his limbs, but sleeping 

 most of the time, a sleep which finally be- 

 comes a coma and terminates in the death 

 of the unfortunate victim. 



In the colonization of Africa one of the 

 most important problems is the extermi- 

 nation of this dreaded disease, which is 

 making constant inroads upon the native 

 population, and which in some districts 

 has carried off more than one half of the 



inhabitants. This increasing prevalence 

 of the disease led the German government 

 to send Professor Koch on a special ex- 

 pedition for its study. Excellent work in 

 this direction has also been done by Eng- 

 lish scientists, especially the Liverpool 

 School of Tropical Medicine, as well as by 

 the French and Portuguese. 



Unfortunately, the treatment of sleep- 

 ing sickness and of the various trypano- 

 soma diseases has been exceedingly unsatis- 

 factorj', but from the work accomplished 

 by various investigators, especially Ehr- 

 lich, Laveran, Mesnil and Nicolle, there is 

 sufficient ground for believing that in the 

 coal-tar or the arsenical preparations will 

 be found specific remedies or at least val- 

 uable auxiliaries. At any rate, the line of 

 research which Ehrlich has been pursuing 

 in this field demonstrates the superiority 

 of the modern methods of treatment, which 

 are based upon purely scientific deduc- 

 tions and not, as was formerly the case, 

 solely upon empirical observations. 



This new system of treatment is founded 

 upon the study of the selective affinity 

 which the various medicaments have for 

 the tissues of the body and for the para- 

 sitic organism that may infe.st it. In the 

 case of most drugs, however, it is difficult 

 and even impossible to understand their 

 selective action, since the changes they 

 produce are for the most part impercept- 

 ible. For this reason Ehrlich at an early 

 period of his studies was led to experi- 

 ment with the anilin colors, since their ef- 

 fect upon those cellular structures for 

 which they have an affinity could be easily 

 determined by their staining property. 



In this connection it may be mentioned 

 that as long ago as 1890 Ehrlich, in collab- 

 oration with Leppmann, published some 

 observations on the pain-relieving qualities 

 of methylenblue, the correctness of which 

 has since been abundantly confirmed 



