596 Inflammation of the Pia Mater. 



basal ganglia and including the latter disturbances of pupillary reaction are to be 

 expected, although this is difficult to determine in animals because the constant 

 movement of the eye makes it scarcely possible to use the ophthalmoscope. The 

 diminution or al)sence of pupillary reaction is comparatively easier to demon- 

 strate in animals in which the proportion of decussating fibers is somewhat large. 

 Diseases of the cortical paths of vision cause no disturbance of pupillary reaction. 



Disturbances of the senses of liearinp^, taste or smell some- 

 times occur in diseases of tlie brain, but tliey can only be discov- 

 ered witli difficulty, if at all, in the dog. 



Literature. Beyer & Lewandowsky, Engelmann's A. f. Phys., 1906, 4.51. — 

 Bickel, Meehanismus d. Bewegungs regulation, 1903. — Dexler, Ergebn. d. Path., 

 1896, III, 2, Abt., 492; 1900, VII, 401; Nervenkrkh. d. Pferdes., 1899.— Dexler & 

 Margulies, Morph. Jahrbuch, 1906, XXXV, 443.— Forster, Die Physiol, u. Pathol, 

 d. Koordination, 1902. — v. Kalischer, Abh. d. Preuss. Akad. d. Wiss. Anhang, 1905. 

 —Marburg, Engelmann's A. f. Phys., 1904; Suppl. Bd., 193, 457.— Monakow, 

 Gehirnpathologie, 1905.— Petren, Skandinav. A. f. Phys., 1902, XIII, 9.— Philippson, 

 Le systeme nerveux des animaux, 1905. — Probst, Sitzungsber. d. K. Akad. d. 

 Wiss. in Wien, 1905, CXIV, 3, Abt.; Monatsschr. f. Psych, u. Neurol., 1900, 387; 

 Arch. f. Psych, u. Nervenkrkh., 1900, 721. — Eothmann, Engelmann's A. f. Phvs., 

 1907, 217.— Schmidt, Z. f. Tm., 1907, XI, 420.— Schrader, Pfliiger's A., XLIV, 175. 

 — Thomassen, Ann., 1893, 241; 1894, 1.— Trendelenburg, Engelmann's A. f. Phys., 

 1906, 1. 



1. Inflammation of the Pia Mater. Leptomeningitis. 



{Acuie men'mfiitis, Enceplialifis, Acute hydrocephalus, Suh-acute 

 encephalitis, Meningo-encephalitis. ) 



Leptomeningitis is the term applied to inflammatory pro- 

 cesses which commence in the pia mater, but which, on anatom- 

 ical grounds, tend to spread to the superficial layers of the brain 

 substance. 



Of the meninges only the arachnoid and the pia mater tend to be- 

 come the seat of primary disease. This may be due to the richness 

 in blood of the pia mater. In view of the fact that small blood vessels 

 penetrate the superficial layers of the brain substance from the pia 

 mater, the diseased process is almost certain to spread to the brain 

 and practically every case is one of meningo-encephalitis. But such 

 cases may be included under the term meningitis in view of the fact 

 that the process starts in the membranes, the brain being affected sec- 

 ondarily. 



Occurrence. Simple acute meningitis occurs more fre- 

 quently in the horse than in other animals and cases are most 

 frequent during the hotter periods of the year. On the other 

 hand, there is no particular difference in the incidence of sec- 

 ondary meningitis in the different species. 



According to Christiani there was an increase in the number of cases of 

 primary meningitis simultaneously with every addition of horses to the stables in 

 the Prussian army and the number of cases increased in proportion to the increase 

 in the number of horses. The disease reaches its maximum during the second and 

 third quarters of the year, just as does the socalled Borna disease. 



