THE NERVOUS SYSTEM. 837 



tunior was composed of fusiform cells, of nerve-gaugliou cells, of tubules 

 and acini lined with cylindrical epithelium, and of more irregular spaces 

 filled with large polygonal cells. 



Coats 1 describes a tumor, three inches in diameter, growing into the 

 third ventricle, the aqueduct of Sylvius, and the fourth ventricle. It 

 was composed of fusiform cells, of tubules lined with cylindrical epi- 

 thelium, of irregular masses of epithelium, of cartilage, and of smooth 

 muscle. 



Hypertrophy with cystic degeneration may occur. 



Haemorrhage into the substance of the gland has been described. 



Hypophysis Cerebri (The Pituitary Body.) 



This structure consists of two lobes ; the anterior lobe is composed of 

 a connective-tissue stronia enclosing cavities which are packed full of 

 nucleated cells of various sizes and shapes, some of them resembling 

 nerve cells ; the posterior lobe is composed of vascular connective tissue. 



Tumors. Weigert a describes a tumor, as large as a hen's egg, which 

 resembled in its structure the normal anterior lobe of the pituitary body, 

 and which he regards as a hypertrophy of that body. Weigert also de- 

 scribes a gummy tumor of the pituitary body as large as a hazelnut. 

 Weichselbaum describes an adenoma of the pituitary body as large as a 

 pigeon's egg, closely resembling the structure of the normal anterior lobe 

 of this body ; a small lipoma ; and a pituitary body with colloid cysts, 

 lined with ciliated epithelium. 



Methods of Preparation of Nerve Tissue for Microscopical Study. 



The general methods of hardening have already been given on pages 16 and 19. 

 For minute study there is no one method of staining and mounting upon which we can 

 rely exclusively for the study of all lesions. A preliminary examination of areas of 

 inflammatory softening, or of the disintegrated tissue in apoplectic clots, or of the new- 

 formed tissue in chronic luzmorrhagic pachymeningitis inter na, may be made by teasing 

 portions of the affected tissues in one-half-per-cent salt solution. Or the tissues in 

 these lesions, or in any others in which fatty degeneration is suspected, may be placed 

 for twenty -four hours in one-per-cent aqueous solution of osmic acid, and then washed 

 and teased in glycerin. In this way the myelin and the fat will be stained brown or 

 black. Secondary and other degenerations of medullated nerves may be studied by 

 soaking the nerves for twenty-four hours in one-per-cent solution of osmic acid, and 

 then staining with picrocarmine and teasing and mounting in glycerin. 



To demonstrate the presence of miliary aneurisms in or about apoplectic clots, it 

 is usually necessary to macerate the brain tissue in water until the nerve elements dis- 

 integrate, and they may then be washed away under a stream of water, leaving the 

 blood-vessels with their aneurisms exposed. 



Marches Method. For studying early stages of degeneration in medullated nerve 

 fibres this method is invaluable. It depends upon the fact that while myelin and fat 

 both stain black, when the fresh nerve fibres are placed directly into osmic acid, a pre- 

 liminary soaking in a solution of potassium bichromate so affects the tissue that the 

 myelin sheaths of normal fibres no longer impregnate with osmiun. the fat droplets 

 alone staining. 



1 Trans. London Path. Soc., xxxviii. * Virch. Arch., Ixv., p. 219. 



