12 CLINICAL APPLIED ANATOMY. 



In cellulitis the infection seems to originate and to spread 

 chiefly in the subcutaneous tissues ; in erysipelas the infection 

 occurs and spreads chiefly in the skin. In cellulitis the skin 

 becomes rapidly cut off from its blood supply, so that it has a 

 tendency to slough, while at the same time death of the 

 subcutaneous tissues is the rule ; in erysipelas, even if the 

 inflammation is sufficiently severe to induce the formation of 

 bullse, no loss of tissue occurs except of the most superficial 

 layers of epithelium. In cellulitis the streptococcus travels by 

 means of both lymphatic and venous channels, and red lines of 

 inflamed lymphatic vessels extending to the first chain of glands 

 are not infrequent ; in erysipelas the streptococcus wanders in 

 the fine cutaneous lymphatic capillaries, and there is no 

 lymphangitis, although always lymphadenitis of the first chain 

 of glands. 



Tetanus. Tetanus is due to the entrance of tetanus bacilli 

 into the tissues and the action of their toxins upon the central 

 nervous system. Owing to the anaerobic nature of the organism, 

 the bacilli are unable to grow upon small and superficial wounds ; 

 hence punctured wounds which lodge bacteria deep in the tissues 

 place them in a soil well-fitted for their vital activity. Since 

 garden mould, road refuse, and similar materials form the chief 

 habitat of the bacilli, punctured wounds of the hands and feet 

 from sharp pointed metallic bodies and lacerated wounds of the 

 head, caused chiefly by falls from vehicles, are those which are 

 not infrequently followed by the development of tetanus. 



It is perhaps needless to say that wounds in the web between 

 the thumb and the index finger are not more liable to give origin 

 to tetanus than are wounds elsewhere, except from the fact that 

 the hands so often come into contact with the material 

 containing the specific virus. The bacilli remain localised at 

 the point of infection ; it is very rare indeed for them to wander 

 into the blood stream and be disseminated by this means, their 

 anaerobic nature being again an obstacle to their migration. 



There is little doubt that the toxin gains access to the central 

 nervous system by way of the trunks of the peripheral nerves, 



