1902.] The Inter-relationship of Variola and Vaccinia. 



125 



with a sterilised lancet, and their fluid contents received into fine capil- 

 lary tubes, which were subsequently sealed in the flame of a spirit lamp 

 to admit of transport. This operation, however, is a most laborious 

 one, and was subsequently abandoned, at my suggestion, in favour of 

 collection, in the post-mortem room, of vesicle pulp at a suitable stage 

 of the eruption, by means of a small Yolkmann's spoon, after the 

 fashion now invariably used in the Government lymph laboratories in 

 obtaining, from the calf, material for the production of glycerinated 

 lymph. 



After removal from the body the small-pox pulp is first carefully 

 weighed, and then ground up in a small glass mortar, with the gradual 

 addition of usually four times its weight of a sterilised 50 per cent, 

 solution of pure glycerine in normal saline solution. After thorough 

 emulsification, what is not required for immediate use is stored in 

 tubes, resembling small test-tubes, which are then corked, sealed 

 with liquefied paraffin to which carbolic acid has been added, and set 

 aside in a chamber kept at a temperature a few degrees above freezing- 

 point. Both storage-tubes and corks are sterilised before use. 



Bacteriological examination by the method of plate-culture often 

 shows a comparatively small number of extraneous micro-organisms in 

 a specimen of small-pox emulsion prepared in the manner described, 

 but whenever possible it has been stored at a temperature of about 

 15° C. for some weeks prior to using it for inoculation. 



Species and Age of Monkeys Inoculated. 



For my original experiments on the transference of human small- 

 pox to the monkey, a brief account of which was presented to the 

 Eoyal Society in 1893, I employed the rhcesus monkey, for the reason 

 that Professor Sherrington and myself had, at the time, a stock of these 

 animals, which had been obtained for other experimental work. Having 

 at that time obtained successful results in every one of my inocula- 

 tions, I employed the same species of monkey in the greater number of 

 the experiments comprised in the present research. As, however, 

 during the progress of the work I learnt that Dr. Eilerts de Haan, who, 

 in Batavia, had been working on similar lines to myself, had made use 

 most successfully of the macaque monkey, I also obtained a few speci- 

 mens of this species, in order to compare the results of variolation 

 in these animals with those that I had previously observed in the 

 rhcesus monkey. But after two or three inoculations of the macaque 

 with small-pox material, I came to the conclusion that the results fol- 

 lowing on the operation were not ordinarily as typical as in those 

 experiments in which rhcesus monkeys had been employed. At the 

 same time the macaque is in this country more expensive and more 

 difficult to obtain than the rhcesus, so that I reverted to the use of the 

 latter species in subsequent work. 



