ADVENTITIOUS GROWTHS. 358 



and substance of the brain. When it is met with it is usiiall}^ 

 as part of a general infective condition rather than as a 

 primary diseased state of these structures. Whether it is 

 rapid or slow of growth depends much upon the form which it 

 takes, and the general condition of which the cerebral chano-c 

 IS merely symptomatic. 



Glioma. — This is the term applied to an abnormal growth 

 in association with the connective-tissue of the cerebral matter, 

 the neuroglia. Both in its general appearance and intimate 

 structure, it seems simply hyperplasia of this material; at 

 least, there is in its composition an extra amount of this, 

 having mingled with it certain peculiar cell-elements much 

 resembling those of sarcoma of the smaller-celled variety. 



Its existence, of varying extent or bulk, I have encountered 

 on several occasions in connection with the cerebellum. 

 In no case was the tumour well defined, but it shaded off 

 gradually into the healthy surrounding structure ; the extent 

 of the growth, and its steady development in several of these 

 instances, inducing recurring disturbance with perceptible 

 thinning of the cranial bones. 



Osseous Tumours. — These, when associated and interfering 

 with the cranial structures, are usually as growths springing 

 from, or which have sprung from, the inner table of the cranial 

 bones, chiefly the temporal. In form they are rounded and 

 nodulated, often attached by a well-defined pedicle ; their physi- 

 cal appearance when large — and they have become detached, 

 occupying the brain-space, the cerebral matter having been 

 removed through absorption arising from their pressure — has 

 sometimes caused them to be regarded as specimens of ossified 

 brain-substance. In intimate composition they are of the 

 nature of dense, compact bone-structure, ivory-looking, and 

 free from the ordinary bone-cavities or canals, very much re- 

 sembling the dental-like growths more frequently seen attached 

 to the outer table of the same bone, and, like them, may owe 

 their origin to perverted development of dental pulps. 



The most frequently observed adventitious developments in 

 the brain of the horse are probably those kno-\vn as concentric 

 amylaceous corpuscles, or cholesteatomatous growths, found in 

 connection with the vascular structures or choroid plexuses of 

 the lateral ventricles. The intimate structure of these growths 



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