PARTI.] Methods Adopted for Continuous Examination of Blood. 67 



The requirements of the case appeared to be sufficiently met by adopting the 

 following methods for the immediate examinations of blood. Specimens of blood 

 were placed under thin covering-glasses, individual specimens being prepared without 

 any re-agent, mounted in acetate of potash after exposure to the vapour of a two 

 per cent, solution of osmic acid, or mounted in acetate of potash or acetate of soda 

 without previous exposure to the osmic fumes. 



For continuous observations on the changes taking place in the blood after 

 its removal from the body, wax-cells were employed. A small drop of blood having 

 been received on the centre of a carefully cleaned covering-glass, the latter was 

 pressed down on the wax-cell and hermetically sealed. The cell was deep enough 

 to prevent the blood coming in contact with the slide, and therefore allowed of its 

 free exposure to the included air. 



This form of wax-cell is a modification of that employed by Strieker in similar 

 investigations on the blood, and is identical with that described by Berkeley as 

 specially adapted for observations on the development of fungi. The great 

 advantage of the method is, that, when once the specimens have been carefully sealed, 

 large numbers of cells may be retained in perfect condition for examination without 

 calling for the employment of the moist chamber and its inherent fallacies, arising 

 from the constant possibility of the introduction of extraneous elements into the 

 material under observation. The effect of any such cells in facilitating observation 

 may be judged of by the fact that by their means specimens of blood have been 

 kept in a condition for continuous observation for nearly three months at a time. 

 That sufficient air is included in them to allow of developments taking place in 

 the isolated droplet of blood may be demonstrated by the results of certain 

 observations to be hereafter referred to. 



The specimens of blood during life were generally derived from the point of 

 one of the fingers of the patient (which had been carefully washed with spirit or 

 clean water and thoroughly dried) by pricking it with a needle. Those after death 

 were usually obtained from one of the chambers of the heart. 



Having briefly explained the methods which have been adopted in carrying 

 out these observations, we now proceed to a description of the results obtained 

 under these conditions. 



I.— Appearances presented by the blood, when treated with osmic acid and acetate 



of potash. 



In osmic acid preparations of cholera blood the red corpuscles appeared unaltered 

 in most cases ; in one or two they conveyed an undefined impression of softness. 

 Few leucocytes were present as a rule, but in one specimen they were present in 

 some numbers, along with other cells of considerably larger size and extremely 

 delicate in outline and structure. Not the faintest trace of bacteria was detected 



