MORBID ANATOMY 



■67 



ij III. Morbid 

 anatomy. The usual 

 direct ana t o m i c a 1 

 changes following the 

 invasion of tubercle 

 bacteria are the forma- 

 tion of nodules or 

 tubercles. A tubercle 

 has been defined as, 

 "a small nonvascular 

 nodule compose d o f 

 cells varying in form 

 and size with some 

 basement substa nee 

 between the m a n d 

 with an inherent ten- 

 dency to undergo 

 central necrosis. ' ' In 

 a large numbe r o f 

 cases the individual Fig. 24. Right lateral aspect of posterior 



tubercles are distinct half of steer's head, {a) lower jaw. (b) ear 



. .. . passage. [c) horn, id) styloid process of 



and easilj' recogmz- -^ * . ; ^ 



able while in others 

 they are coales c e d 

 forming a mass of 

 necrotic tissue. The 



occipital bone, (e) parotid gland, (f) sub- 

 maxillary gland. A. right parotid lymph 

 gland. B. right post maxillary lymph 

 gland. C. right submaxillary lymph gland. 

 Lvniph glands often the scat of tubercular de- 



1 • .^ posits. (Smith.) 



lesions vary, there- ^ ^ 



fore, from well isolated minute or larger nodules to masses or 

 cavities containing a purulent, caseous, or calcified substance. 

 The location of the primary lesion depends upon the chan- 

 nel of infection. If the specific organisms are lodged in the 

 oral cavity or pharynx they may, through an accidental abra- 

 sion of the mucosa, be taken to some of the lymphatic glands 

 about the head : if they are taken directly through the respira- 

 tory passages into the lungs they either develop nodules in the 

 lung tissue proper, or they are carried through the lymphatic 

 system to the lymph glands draining the lungs where the lesions 

 first appear. If the specific bacteria are first lodged in the 



