THE NERVOUS SYSTEM. 827 



or smaller black droplets scattered along a broken or degenerated axis 

 cylinder. There may be some increase in the connective tissue. The 

 sheath of Schwanu is usually intact. It is of interest to note that in a 

 number of cases (as yet too few to warrant general conclusions) changes 

 have been found in the cells of the anterior horn analogous to those 

 found after injury to motor nerves (page 803). The muscles supplied 

 by the affected nerves show various stages of atrophy. The cord and 

 nieninges usually remain normal. In some cases a spinal meningitis 

 and more or less myelitis have been described. 



CHRONIC INFLAMMATION OF THE BRAIN, CORD, AND SERVES. 



While this term should be applied only to a primary increase in the 

 neuroglia elements at the expense of the parenchymatous, thus making 

 the degeneration of the nervous tissue proper entirely secondary, it is 

 very difficult always to eliminate the possibility of preceding degenera- 

 tive changes. Histologically the lesion consists in a proliferation of the 

 ueuroglia elements. The ueuroglia cells increase in number, some of the 

 new-formed cells having many processes, others few. In the early cellu- 

 lar stage of its formation the proliferative area is soft and gelatinous, 

 and tends to increase the size of the part. With further progress of the 

 sclerosis, there is a disproportionate development of fibres attached to 

 the cells, and finally of fibres independent of cells. With the increase 

 of fibres the affected area becomes firmer, making a sort of dense /elt- 

 work of interlacing fibrils. In this meshwork are found nerve fibres in 

 various stages of degeneration. 



Chronic Interstitial Encephalitis Sclerosis. This lesion of the brain 

 tissue may occur diffusely, occupying an entire lobe or more or less of the 

 whole brain, or in circumscribed small areas. It consists essentially in 

 an increase of the connective-tissue elements, the neuroglia, and an atro- 

 phy of the nerve elements, particularly the ganglion cells and the medul- 

 lary sheaths of the nerves. With these changes are usually associated 

 the formation of Gluge's corpuscles, corpora amylacea, granular and 

 fatty degeneration of the nerve elements, and thickening and prolifera- 

 tion of cells of the walls of the blood-vessels. The areas of sclerosis may 

 be very dense and hard, or gelatinous in consistence. 



The diffuse form of sclerosis is most frequently seen in general pare- 

 sis of the insane, and not infrequently in the brains of drunkards. 



A peculiar feature of disseminated sclerosis is that the patches, 

 whether in the brain or cord, do not induce the expected secondary 

 degeneration. It is, in fact, uncommon to find secondary degeneration 

 resulting from* even a large patch of sclerosis. This is believed to be due 

 to the fact that in nearly all of the patches the axis cylinders persist even 

 after complete destruction of the medullary sheaths. 



The circumscribed form of sclerosis, multiple sclerosis (scUrose en 

 plaque}, is much more common than the diffuse form, and may possibly 

 occur in the brain alone, or more commonly is associated with a similar 



