ioo MICRO-ORGANISMS AND DISEASE [chaP. 



20,000 were subcutaneously injected into a rabbit. The 

 animal died in about twenty hours. The bacilli in the 

 heart's blood were then counted by the ordinary method of 

 gelatine plate-cultivation, and it was found that their 

 number per cubic centimetre of heart's blood amounted to 

 14,150,000. The weight of the rabbit was 1,250 grammes, 

 and taking eighty-three grammes (jy) as the amount of 

 blood present in the animal's body, and assuming that the 

 bacilli were more or less uniformly distributed through the 

 blood, it follows that the total blood contained about 

 1,200,000,000 of the bacilli. This would mean that each 

 one of the 20,000 bacilh injected had given origin to a host 

 of 60,000 bacilli in twenty hours. 



The manner in which the individuals of the same species 

 divide varies considerably ; thus in the streptococcus scar- 

 latinae and str. pyogenes the writer has observed that in 

 gelatine some of the elements of a colony increase rapidly 

 to five, six, and more times the size of a typical coccus, 

 grow, in fact, into a ball of great size, then a cleft appears 

 by which the organism splits up into two demilunes, then 

 each of these again divides under a right angle to the 

 former line of division, so that the original ball is divided 

 into four quarters, each of which separates gradually from 

 its neighbour and becomes more or less spherical, and a 

 further division into two, and even into four, cocci of the 

 average size takes place. But the above mode of division 

 does not take place everywhere in the preparation, for many 

 of the typical cocci only slightly enlarge and then divide 

 into two, thus forming a diplococcus ; each of these divides 

 again transversely, and thus a chain of four minute cocci is 

 the result. 



In broth cultures the writer has observed, as a rule, the 

 latter mode of division, though also here occasionally an 



