598 luliamuiation of the Pia jMater. 



generally accepted idea that the progeny of animals subject to 

 staggers are more easily affected than the progeny of healthy 

 animals. 



Secondary meningitis may lie due to a large variety of 

 causes. The most common cause is probably a pyogenic bac- 

 terium of some kind or the streptococcus of strangles. In cat- 

 tle cases due to the bacillus of tuberculosis are comparatively 

 common. Koske proved that the meningitis met with in cases 

 of infectious rhinitis in the pig (see page 4) was due to the 

 bacillus pyocyaneus. Many other organisms may be responsi- 

 ble for the condition. 



The infection may be carried into the cranium through 

 wounds resulting from kicks, trepanning, etc. Not rarely men- 

 ingitis may be due to disease in neighboring parts ; tuberculosis 

 of the cranial bones in cattle, caries of the petrous temporal 

 bone in dogs and pigs, and more rarely in horses, necrosis of the 

 atlas may be the starting point, the infection reaching the men- 

 inges either directly or by way of the blood vessels or nerves. 

 Similarly general inflammation of the eye, diseases of the mid- 

 dle ear (in dogs and swine), chronic catarrh of the nasal sinuses 

 in the horse and cattle, deep-seated inflammation of the wall of 

 the pharynx, suppuration in the parotid region may lead to 

 acute meningitis. Foreign bodies penetrating the cranial cav- 

 ity from the pharynx may also act as vehicles of infection (Dur- 

 rechou). Finally, rupture of a cerebral abscess on the surface 

 of the brain or in the ventricles may cause purulent inflam- 

 mation. 



Infective material may reach the meninges by way of the 

 blood stream in cases of strangles, ulcerative endocarditis, tu- 

 berculosis, injuries to the stomach (Kabieaux), etc., and also 

 from gangrenous foci in the lungs and possibly also from worm 

 nodules in the intestine (Hess). 



Frankel's discoveries regarding the presence of bacteria in the brain in gen- 

 eral infectious diseases are interesting. Bacteria, and in lo% of cases pyogenic 

 bacteria, could be demonstrated in the brain of men that had died from suppurative 

 or other bacterial diseases of some kind, but who during life had shown no symp- 

 toms of brain disturliance. Microscopic examination revealed the presence of 

 small inflammatory, necrotic and hemorrhagic centers and a very slight degree of 

 perivascular infiltration. In favorable cases these lesions may disappear without 

 any symptoms having been shown or in others they may sooner or later lead to 

 meningitis. 



In occasional cases secondary meningitis may be due to the 

 invasion by animal parasites, such as the larvie of the Scleros- 

 toma armatum, the gastrophilus in the horse, CEstrus bovis in 

 cattle, the larvae of ticks and ccenurus cysts in the sheep, cysti- 

 cerci in the dog and pig. 



Pathogenesis. The inflammation of the membranes and 

 the cortex causes an active hyperemia which is accompanied, 



