18 BULLETIN 1449, U. S. DEPARTMENT OF AGRICULTURE 
thickenings. Thirteen hundred and fifteen such nodules in one old 
cow were recorded by Morot. Neurofibromas have also been reported 
in horses and pigs. 
Among the rarer forms of neuromas and neurofibromas in man 
may be mentioned the painful subcutaneous tubercle, ganglion 
neuromas, and the multiple molluscum fibrosum, a nodular elevation 
of the skin. 
GLIOMA 
Definition. — Gliomas are neoplasms which grow from the cells of 
the neuroglia or glia, the supporting tissue of the central nervous 
system. Several authenticated cases have been recorded by Kitt (11) 
in dogs and also in other domestic animals. In man it is the most 
common neoplasm of the brain. 
■Appearance. — Glioma is usually a solitary neoplasm, rounded or 
oval, but difficult to distinguish from the normal brain. It is 
usually about the size of a cherry but may become as big as an apple. 
It is either soft or moderately firm and usually grayish white, but at 
times is dark red, when it appears sharply defined from the brain 
substance. In the last case it is traversed by numerous blood vessels 
and may contain hemorrhagic areas. 
/Seats. — Gliomas occur most frequently in the brain, less frequently 
in the spinal cord, and rather rarely in the retina. Gliomas of the 
brain and cord do not metastasize to other organs, but they may in- 
vade or disseminate in the tissue where they originally started. In 
their pure state gliomas are benign except for their situation; they 
may become dangerous by causing intercranial pressure or producing 
paralysis by pressure on a motor center, or may cause sudden death 
by hemorrhage. The retinal glioma is an extremely malignant and 
more rapidly growing neoplasm. Another rapidly growing glioma 
occurs in the adrenals, and is rarely found in the nervous system 
proper. The adrenal gliomas have a tendency to metastasize to the 
lymph glands and the liver. In the retroperitoneal region there is 
also a benign form of glioma originating from the sympathetic nerv- 
ous s}^stem which from a predominance of large ganglion cells is 
called ganglioneuroma. 
Structure. — Under the microscope neuroma consists mainly of 
small, round cells which are larger than ordinary glia cells, with 
prominent round or oval nuclei and numerous delicate branching 
processes. Some of the cells may possess a large amount of cytoplasm 
and several nuclei. The interstitial glia or neuroglia framework may 
consist of such delicate fibrils that the structure is as cellular in ap- 
pearance as a sarcoma, and for that reason gliomas are often spoken 
of as the sarcomas of the brain. It must be borne in mind that the 
glia elements are of ectodermal and not entodermal origin. The 
gliomas starting in the retina are very cellular in structure. Some 
gliomas may have an abundance but never a predominance of neu- 
roglia fibers, while the glioma of the sjonpathetic system has a con- 
siderable number of large ganglion cells, from which it receives the 
name ganglion-cell neuroma. In some gliomas groups of ependyma 
cells form rosettes around the blood vessels, resembling the tubules 
of adenoma. These neoplasms are called gliosarcomas by some 
pathologists. 
