BLOOD CULTURES 143 



venous, but not the arterial, circulation. Broth tubes 

 or agar plates are inseminated each with 0-5 c.c. of the 

 blood. Douglas and Colebrook recommend trypsin broth 

 for this purpose, i.e. broth to which 5 per cent, of Allen 

 and Hanbury's compound solution of trypsin has been 

 added after sterilisation. 



Although the modem methods of isolation and cultivation have 

 rendered immense service to bacteriology, they have also had the 

 effect of diminishing the attention paid to the exact morphology 

 and biology of organisms. At the present time there is a tendency 

 to investigate bacteria en masse rather than to study them as indi- 

 vidual living forms. As the late Marshall Ward remarked : 



" The introduction and gradual specialisation of Koch's method 

 of rapid isolation of colonies encouraged the very dangers it 

 was primarily invented to avoid. It was soon discovered that 

 pure cultures could be obtained so readily that the characteristic 

 differences of the colonies in the mass could presumably be made 

 use of for diagnostic purposes, and a school of bacteriologists arose 

 who no longer thought it necessary to patiently follow the beha- 

 viour of the single spore or bacillus under the microscope, but 

 regarded it as sufficient to describe the form, colour, markings, 

 and physiological changes of the bacterial colonies themselves 

 on and in different media, and were content to remove specimens 

 occasionally, dry and stain them, and describe their forms and 

 sizes as they appeared under these conditions. To the botanist, 

 and from the point of view of scientific morphology, this mode of 

 procedure may be compared to what would happen if we were 

 to frame our notions of species of oak or beech according to their 

 behaviour in pure forests, or of grass or clover according to the 

 appearance of the fields and prairies composed more or less entirely 

 of it, or and this is a more apt comparison, because we can 

 obtain colonies as pure as those of the bacteriologist of a mould 

 fungus according to the shape, size, and colour, etc., of the patches 

 which grow on bread, jam, gelatine, and so forth." 



Examination of Living Organisms 



Examination in the fresh and living condition is an 

 essential procedure in the investigation of micro -organ- 



