The Vet. Book 



They belong to the Protophyta and can be 

 cultivated on suitable media outside the body. 

 They are divided into disease-producing and non- 

 disease-producing classes, and some require 

 oxygen for their growth, whilst others its com- 

 plete exclusion. For instance, the germs of 

 anthrax, when circulating in the blood of the living 

 animal, exist in the form of minute rods, and these 

 rods, in order to multiply, divide transversely, 

 but directly the blood is exposed to the air, the 

 organisms form long chains of spores as a method 

 of multiplication, and these spores have remarkable 

 powers of vitality ; hence the reason why an 

 anthrax grave may constitute a source of infection 

 for an indefinite period. A singular feature in 

 connection with the germs of anthrax is their 

 immediate destruction by the organisms of putre- 

 faction, and this is one reason why the germs of 

 anthrax are so frequently absent from the blood. 

 Some organisms are capable of distribution through 

 the air, the germs of Tuberculosis forming a good 

 example, and this is spoken of as a volatile poison. 

 The methods of multiplication are usually of a 

 very simple character — the parent organism usually 

 dividing and sub-dividing. The destruction of 

 germs is, as a rule, easier than that of their spores, 

 but there are agents capable of destroying both, 

 provided that a sufficient length of time is allowed. 

 Extremes of heat and cold — more especially the 

 former — usually act adversely upon them, but 



xxxii 



