522 DR JAMES W. DAWSON ON 



The older patches are firmer than the normal substance of the brain or cord, but 

 recent patches are occasionally seen which are gelatinous and softer than the normal 

 tissues. The chief macroscopical characters of the lesions are their insular character, 

 their irregular dissemination, the absence of secondary ascending and descending 

 sclerosis in most cases. This feature — the absence of secondary degeneration — 

 sharply distinguishes disseminated sclerosis of the spinal cord from other multiple 

 lesions, such as disseminated myelitis and multiple syphilitic lesions. 



" Under the microscope a striking feature of many patches is their sharply 

 defined nature. This feature is well seen in the sections stained according to 

 Weigert's method. Examination under a high power shows that medullated nerve 

 fibres are generally absent in the sclerotic patches ; but sometimes at the border of a 

 patch there is a zone in which the medullated fibres are present, though scanty. At 

 the periphery of some patches compound granular cells are found, along with indica- 

 tions that the morbid process is still active. In the patches of sclerosis the axis 

 cylinders of the nerve fibres are very often present though the medullated sheaths 

 have disappeared. The ganglion cells of the grey matter escape degeneration for a 

 long period in the diseased patch ; but at a very advanced stage they, like the axis 

 cylinders, may finally disappear. The neuroglia connective tissue in a diseased patch 

 is often greatly increased and converted into a dense fibrous tissue. Spider cells 

 may be present, but the neuroglia is not richer in nuclei than in the normal condition. 

 In other cases the neuroglia, though increased in amount, has an amorphous or 

 homogeneous appearance under the microscope. In some patches the nerve fibres 

 have degenerated, and spaces are left in the neuroglia from which the true nerve 

 elements have disappeared, but the connective tissue itself has not proliferated. 

 Compound granular cells are often present, especially at the periphery of a patch. 

 They are most numerous in recent patches, but may be absent in old patches. Often 

 there are large epithelial-like cells in cavities near blood-vessels. The walls of the 

 blood-vessels in some cases appear normal ; in some cases they are thickened and 

 hyaline or present evidence of endo- or peri-arteritis ; in other cases (in recent 

 patches) the peri-vascular lymph sheaths are filled with round cells, compound 

 granular cells, and fat globules. Often a large altered blood-vessel is found in the 

 centre of a patch of sclerosis. 



"Four forms of sclerosed patches may therefore be met with: (l) patches in 

 which nerve fibres have degenerated, leaving sieve-like small cavities in the neuroglia, 

 whilst the neuroglia connective tissue itself has increased very little ; (2) patches in 

 which there is marked proliferation of the neuroglia along with degeneration of nerve 

 fibres ; (3) patches presenting diffuse proliferation of neuroglia, whilst the nerve 

 fibres and cells persist ; (4) recent patches presenting changes very similar to those 

 of cerebral softening — products of nerve degeneration and myelin drops, fat granular 

 cells, and distension of the peri-vascular sheath of the blood-vessels with round cells. 

 A point of importance is the presence of patches in various stages of development, 



