514 SUMMARY OF CURRENT RESEARCHES RELATING TO 



quantity of melted saline agar is poured. For an ordinary test-tube 

 1 c.cm. is ample. The agar is a 1|^ p.c. solution in 0*85 p.c. NaCl 

 solution. No alkali is added. The tubes are then plugged and sterilized 

 in the autoclave. Shortly before the tubes are to be used the agar is 

 melted l)y immersing the lower end of the tube in boiling water, and the 

 melted agar is allowed to run up the walls of the tube so as to coat them 

 with a thin film. The excess of agar may be allowed to run back to the 

 bottom of the tube, or, if it be considerable, it may be poured away after 

 removal of the plug. 



Either the whole of the inner surface of the tube may thus be coated 

 or there may be left uncoated a longitudinal strip running from the 

 mouth of the tube down some three-quarters of its length and having a 

 width of about one-third of the circumference of the tube. In the 

 former case the whole clot will detach itself from the glass and cither 

 sink to the bottom or remain suspended by delicate attachments to the 

 upper pole. In the latter case the clot will almost always adhere firmly 

 to the uncoated strip of glass while separating everywhere else. The 

 serum which separates out is practically always free from any visible 

 trace of hsemoglobin, and it may be left in contact with the clot for 

 several days without acquiring a pink tinge. The coagulation of the 

 blood appears to be slightly delayed by contact with agar, and the 

 quantity of serum obtained in a given time is usually rather less than is 

 the case of a perfect automatic separation from a plain glass surface. 

 But both these disadvantages, in themselves not important, may, if 

 desired, be counteracted by placing the tubes in the incubator at 37° C. 

 for one or two hours after collection of the ])lood. If this has liecn 

 performed aseptically the high temperature will do no harm. Once 

 coagulation has taken place separation and contraction occur with 

 striking rapidity. The action of the agar film appears to be purely 

 mechanical. The clot adheres firmly to the film, and the serum which 

 first exudes from the clot filters through the film or passes through 

 cracks in it and separates the film from the wall of the tube. The ad- 

 hesion of the agar to the clot is often clearly to be seen at the lower pole 

 of the clot when a ping of agar has been left at the l)ottom of the tulie ; 

 for the plug can be seen capping the lower pole of the clot and drawn 

 up by it away from the floor of the tube. 



Vaccination in Typhus Fever.* — Muriel Robertson has carried out 

 a sei'ies of experiments on monkeys with a vaccine derived from the 

 coccus grown from cases of typhus in Belfast by Dr. Penfold in r.»14. 

 The monkeys received injections of 150 million, 1000 million, and 

 10,000 million killed cocci, and finally a living emulsion of 2000 million 

 oi'ganisms. It was found, however, that the animals so inoculated did 

 not acquire any immunity against a subsequent intraperitoneal inocula- 

 tion of l)lood from a typhus patient. A similar coccus to Penfold's 

 organism was isolated from the blood of two typhus cases examined, but 

 no evidence was obtained of a causal connexion between the coccus found 

 in the blood and the clinical condition known as typhus fever. 



* Jouru. Pathol, and Bacteriol., xxi. (1917) pp. 171-83. 



