266 DISEASES OF THE BRAIN. 



and the determination of its locality, likewise with certain exceptions, 

 is impossible.") This apparent paradox is due to the fact that, in spite 

 of the absence of constant symptoms pathognomonic of tumors of the 

 brain, in most cases the diagnosis may be made partly from the eti- 

 ology, partly from the location of the disease at a point where other 

 local diseases are rare and tumors common, and, lastly, partly from the 

 peculiarities of the entire course of the disease. 



The important evidence furnished by the etiology is chiefly nega- 

 tive. In every case of brain-disease we should make it a rule to seek 

 for the exciting cause by obtaining an exact history of the case. If 

 we thus find that the patient has had no injury of the head, that he 

 has no caries of the petrous bone, no hypertrophy or valvular disease 

 of the heart, and probably also no degeneration of the arteries ; in 

 short, if we can find no cause for the disease, our suspicions must first 

 turn to a tumor of the brain. Before speaking of the cases where 

 cerebral tumors can be recognized with facility and certainty, I shall 

 say a few words concerning the rare cases wheie they induce no symp- 

 toms, or else have those of severe brain-disease, but do not give any 

 means of determining that they are caused by a tumor. The tumors 

 with latent course can only be located at parts of the brain where they 

 do not disturb the intercerebral centres of the cranial nerves, or inter- 

 rupt the conduction of excitement in the centripetal and centrifugal 

 brain-filaments, that is, chiefly in the extensive medullary masses of the 

 cerebrum. At this part tumors often attain a large size without in- 

 ducing local symptoms (herdsymptome), while at most parts of the 

 base of the brain, and in the vicinity of the large ganglia, even the 

 smallest tumors are accompanied by these symptoms. But even in 

 the cerebrum only those tumors run a latent course which grow slowly, 

 and are not so vascular as to swell at times from the vessels being 

 overfilled, and at others to decrease in size from containing less blood. 

 To explain the remarkable but very certain fact that the symptoms ac- 

 companying rapidly-growing tumors are not unfrequently absent in 

 those that grow slowly, a certain " power of accommodation " has been 

 ascribed to the brain, which enabled it to accustom itself to gradually- 

 increased pressure. I consider the following explanation more satis- 

 factory : In tumors that grow rapidly there is a compression of the 

 capillaries and a loss of function of those parts of the brain where 

 they are located. On the contrary, in the vicinity of slowly-growing 

 tumors there is atrophy of the brain-substance, and its shrinkage sup- 

 plies as much room as is lost by the growth of the tumor. Under these 

 circumstances the capillaries of the affected part of the brain are not 

 compressed, and its function not disturbed. Perhaps the presence or 

 absence of local symptoms (herdsymptome), in tumors of the cere- 



