288 
The Infe-history of Trypanosoma equiperdum. 
By J. E. SALVIN Moorg, Professor of Experimental and Pathological Cytology, 
University of Liverpool, and ANTON BREINL, Director of the Runcorn 
Research Laboratories, Liverpool School of Tropical Medicine. 
(Communicated by Sir Rubert Boyce, F.R.S. Received March 9,—Read March 12, 
1908.) 
[PLaTEs 8 AND 9.| 
In May, 1907, we* showed that the study of the parasite of sleeping sickness 
(Trypanosoma gambiense, Dutton), as it appears in the blood of rats artificially 
infected with the disease, revealed a cyclical metamorphosis, and that this 
cyclical metamorphosis corresponded closely to the alternating phases of 
presence and absence of trypanosomes in the blood. At the same time it 
was found that the cyclical metamorphosis in the parasites corresponded less 
closely, but still unmistakably corresponded, with the successive alternations 
of condition that characterise the clinical aspects of the malady in the host. 
The features of the life-cycle of the parasites of sleeping sickness as they 
appear in the blood during infection in rats are remarkable, and may be 
briefly repeated for reference. From the time of inoculation the parasites 
multiply in the blood through amitotic division of the nucleus,} and longi- 
* Note on “The Life-history of the Parasite of Sleeping Sickness,” ‘ Lancet,’ p. 1219, 
May 4, 1907; “The Cytology of the Trypanosomes,” Part I, ‘Ann. Trop. Med. and 
Parasitology,’ vol. 1, No. 3. 
What is called the nucleus of those trypanosomes with which we are acquainted, 
when fixed in Flemming’s fluid, or by any other appropriate method, does not appear 
to show any trace of chromosomes. It consists of a central sphere, intra-nuclear 
centrosome (Salvin Moore and Breinl, loc. cit.) enclosed by a mass of substance, which 
may be made to stain in a different manner from the sphere. When the nucleus divides, 
the interior sphere first elongates, then assumes a dumb-bell shape, and finally breaks 
into two spheres, the outer substance collecting these new centres (intra-nuclear centro- 
somes), so as to form two smaller nuclei with the same structure and appearance as the 
first. The reasons for regarding this structure as a nucleus, @.e, as equivalent in a 
morphological sense to the nuclei of other protozoa, and protophyte bodies, and to 
the nuclei of the metazoa and metaphites, are simply these: The structure in question 
bears a superficial resemblance to the nuclei with which biologists are familiar. It 
divides in the amitotic fashion, ze, as if it were a viscous drop, and owing to the 
existence of the intra-nuclear centrosome, and to the manner in which this body appears 
in. tiate the fission, the whole structure bears a close and striking resemblance to 
the undoubted nuclei of some unicellular organisms, such as Euglena. There is, how- 
ever, this difference: the nuclei to which that of the trypanosomes bears the closest 
resemblance, such as those of the Euglene, have been found to possess chromosomes. 
Chromosomes have been described as appearing during the divisions of the nuclei of 
