702 C.Miii.tvssini, or iliL- Spinal Cord. 



ai'c said to })1'ovl' tlu' occiiiTciu-i' oi' lalics ilorsalis in the lower animals. 

 For a long time trotting disease (Traberkrankheit) of the sheep, and 

 tlie nervous stage of dourine were thought to correspond with tal)es in 

 man, until histological examinations finally showed that there is no con- 

 nection between them. Frohner claims to have seen cases in the dog 

 exactly simulating tabes, Lienaux and Hendricks record a case in a 

 liorse that closely resembled ta])es both clinicall}^ and histologically ; and 

 Hendricks records a case of locomotor ataxia in a dog. Hamburger 

 found degeneration of the posterior columns in a dog, but the case was 

 not observed clinically. 



These and similar cases do not prove in the least the existence of 

 tabes or a disease like it in animals. The cases that were observed, 

 only clinically furnish no proof because the diagnosis was based simply 

 on the symptoms of sensory disturbance, and sufficient consideration 

 was not given to the fact that similar disturbances may be caused by 

 other lesions of the motor paths, as components of the co-ordinating 

 system (see page 588). Besides the condition of the reflexes is not men- 

 tioned, and in cases where such examination was made (Hendricks) 

 they were found to be exaggerated. No histological evidence of the oc- 

 currence of the disease in animals has been adduced. The degeneration 

 of the posterior columns observed in sheep by Anacker in cases of 

 trotting disease have not been found by investigators Avorking with 

 accurate methods. The case of Lienaux and Hendricks, already men- 

 tioned, merely shows that in this particular case there was disseminat- 

 ed myelitis, which happened to produce a lesion in the cervical portion 

 of the posterior columns with consequent degeneration upwards. It is 

 merely a case of localized disease of the cord associated with the not un- 

 usual ascending degeneration. Hamburger's case in the dog Avas similar 

 in nature. Hutyra & Marek have found pronounced degeneration of 

 the posterior columns in cases of disseminated myelitis in distemper; 

 but there was not the slightest resemblance to tabes. 



6. Compression of the Spinal Cord. Compressio meduUae 



spinalis. 



Compression of the cord is caused by a variety of diseases 

 in wliich tliere is a reduction in the Inmen of tlie vertebral canal. 



Etiology. The primary disease may involve either the tis- 

 sues immediately surronnding- the vertebral column, the verte- 

 bral column itself, the vertebral canal, the membranes of the 

 cord, or the cord. The following diseased conditions may cause 

 compression of the cord. 



Degeneration of the Intervertebral Discs (Enchondrosis 

 interverte1)ralis). Tliis occurs almost exclusively in the dog and 

 was hrst described accurately, clinically and histologically by 

 Dexler. Recently two cases have been observed in the pig by 

 Marek. Nothing definite can he said as to the cause. The fre- 

 quency of the occurrence of the disease increases with age. 

 The occurrence of the degeneration in those parts of the spine 

 that are the most mobile appears to suggest that it may in some 

 cases be caused hy excessive curving, strain, etc., of the spine, 



