350 PHYSIOLOGY CHAP. 



the hyperaesthesia as a phenomenon of dynamogeny, without 

 asserting that these two terms gave any final solution of the 

 problem, which it must be admitted is still totally obscure. 



More recently (1902) Borchert, in H. Munk's laboratory, made 

 further experiments on the effects of dividing the dorsal columns 

 in dogs at different levels of the cord, and investigated the disturb- 

 ances of tactile, painful, and muscular sensibility in the limbs. 

 His experiments, controlled by microscopic examinations, showed 

 that after section of the dorsal columns, not only painful, but also 

 tactile and muscular sensibility (consciousness of position of limbs) 

 persisted, so that there was still some power of localisation. 



This, according to Borchert, disposes of Schiffs theory that 

 tactile impulses can only be conducted by the long fibres of the 

 dorsal columns, while it eliminates the contradiction in the results 

 observed on man and on the dog. Just as man is still capable 

 after degeneration of the dorsal columns, as in tabes dorsalis, of 

 perceiving tactile stimuli, so the dog is not insensitive to them 

 after experimental division of the same columns. 



It follows that tactile sensations must be transmitted by the 

 short intraspinal afferent paths, and that destruction of the dorsal 

 columns (Borchert) causes not a qualitative, but only a quantitative 

 diminution of sensibility. 



Finally we must refer to the work of Petren (1902), who made 

 a careful synthetic review of clinical cases, particularly those with 

 unilateral lesions of the cord due to traumna, spondylitis, syringo- 

 myelia, etc. He concludes that tactile sensibility (pressure) 

 follows two paths in the cord : the one, the long uncrossed path of 

 the dorsal columns; the other associated with the paths of the 

 other forms of cutaneous sensibility. The latter (pain, tempera- 

 ture) first pass through the dorsal horn of the same side, and then 

 cross the median line. For the hind-limbs this decussation is 

 completed by the level of the first lumbar segment, or at latest the 

 twelfth thoracic segment, never lower down. After crossing, these 

 paths run upwards in the external half of the lateral column, but 

 in the higher segments they reach its median half, so that there 

 is within the lateral column a gradual displacement of fibres from 

 without inwards. These sensory paths probably correspond with 

 part of the fibres of the tract of Gowers. 



According to Petren, a unilateral lesion of the cord, when not 

 too low down, only produces crossed anaesthesia. This assumes 

 two forms : either pain and thermal sensibility are altered, while 

 tactile sensibility remains normal ; or all forms of cutaneous sensi- 

 bility are modified. These are the only types found, the first 

 being the most common. 1 



1 EDITORIAL NOTE. The question of sensory conduction in the cord can evi- 

 dently be definitely settled only by observations of the sensory disturbances pro- 

 duced by local spinal lesions in man, as in man alone is it possible to investigate 



