TRYPANOSOMES. 



By MALCOLM EVAN MACGREGOR, E.R.M.S. 



Considering the great amount of attention 

 trypanosomes have demanded, and are still de- 

 manding, in many tropical and semi - tropical 

 countries, it will he the endeavour in this paper 

 not so much to present a scientific or in any wax- 

 thorough description of 

 the organisms called 

 trypanosomes, but more 

 to give a brief survey of 

 a few of the aspects of 

 general interest that are 

 met with in their study. 



Trypanosomes belong, 

 in the animal classifica- 

 tion, to the Phylum 

 Protozoa, and are 

 parasites in the blood of 

 vertebrate animals. They 

 are minute unicellular 

 organisms of somewhat 

 eel-like shape, and range 

 in length very widely: 

 from seven to thirty 

 microns being about the 

 commonest variation. 



Eirst discovered in the 

 \ear 1841, by Valentin, 

 in the blood of a fish, 

 they have since been 

 found in the blood of 

 nearly all vertebrates, and 

 while some species of 

 trypanosomes do little, 

 if any, harm to the ani- 

 mal in whose blood they 

 live, and where they may 

 swarm; other species, if 

 present only in the 

 smallest numbers, pro- 

 duce most terrible results. 



Such diseases, for 

 instance, as sleeping 

 sickness, Nagana (the 

 fly-sickness of cattle in 

 Africa), Dourine (a 

 horse - sickness in India 





TT>t fW^tUunv 



the blood of a trout ; but it was not until 1880 that 

 Evans, working in India discovered the first patho- 

 logical trypanosome. This was the trypanosome that 

 produced the disease in horses and camels, called 

 Surra. Eourteen years afterwards, in 1894, came 



Bruce's discovery of a 

 trypanosome as the 

 cause of Nagana (or fly- 

 sickness) in Africa. 



In 1901, Button dis- 

 covered a trypanosome in 

 the blood of a European 

 in the Gambia, which 

 he appears at first not to 

 have quite realised the 

 significance of. In the 

 May of 190.3, Castellani, 

 while examining the 

 cerebro-spinal fluid of a 

 native suffering from 

 sleeping sickness, dis- 

 covered in this fluid a 

 trypanosome, and it was 

 he who first connected 

 the organism with the 

 disease. 



/acuc'its 





From a Drawing by Count L. tie Sibottr 



Figure 20.i. Trypanosoma gambiense. 

 The most salient structural details of a Trypanosome. 



Morphology. 



The Morphology is 

 extremely simple (see 

 Eigure 203). The body 

 consists of an elongated 

 mass of protoplasm taper- 

 ing anteriorly to a fine 

 point, and ending pos- 

 teriorly rather more 

 blu nth'. The body proto- 

 plasm is often very 

 granular, and often shows 

 vacuoles in it. 



About the centre of the 

 body the structure known 

 as the nucleus is generally 

 situated, but oftentimes 



it is found more anteriorly 



Mai de Caderas, of placed, and at other times it is in quite a posterior 



South America, a human disease that occurs in the position. In shape the nucleus is usually oval 



same country, and many others, are all diseases or resembling the shape of a bean, and stains a 



due to trypanosomes ; so that trypanosomes in dense purple-blue colour with the ordinary 



some parts of the world have to be looked upon as trypanosome stains. The chief function of the 



one of man's deadliest enemies: an enemy over nucleus is thought to be the governing of the 



which, as we shall see later, he has yet been able functions of the protoplasm (the metabolism and 



to get but the smallest victory. katabolism), and it is hence sometimes called the 



It was, as already stated, Valentin in 1841 who " tropho-nucleus " to distinguish it from another 



discovered the first trypanosome, and this he did in small mass of nuclear material that occurs in the 



:: Being the subject-matter of a lecture delivered before the Cambridge Natural History Society, February 20th, 1913. 



197 



