70 MICRO-ORGANISMS AND DISEASE. [CHAP. 



Pohl-Pincus 1 traced their passage through the epidermis at 

 the point of vaccination in the calf. The micrococci are very 

 minute, according to Cohn's estimate 0*0005 mm. and less 

 in diameter, single or in dumb-bells, or in shorter or longer 

 chains, or in small groups. When cultivated on the warm 



FIG. 21. MICROCOCCUS IN THE FRESH LYMPH OF HUMAN SMALL-POX. 



1. Singly. 



2. In dumb-bells. 



3. In short chains. 



stage, they form very long chains and colonies. In connexion 

 with this it must be mentioned, as stated on a former page, 

 that similar micrococci occur also in the fluid contents of 

 vesicles in the skin produced by various non-infective 

 inflammations. To make it sure that the micrococci are the 



FIG. 22. LYMPHATIC VESSEL FROM THE SKIN OF A POCK IN SHEEP-POX. 

 The vessel is filled with micrococci. 



active principle, i.e. the causa morbi, it would be necessary 

 to artificially cultivate them through several generations, 

 and then, by re-inoculating them, to reproduce the 

 disease. This essential link in the evidence is, however, 

 still wanting. 2 



1 Vaccination, Berlin, 1882. 



2 See the prize announcement of the Grocers' Company, London, 1883. 



