Functions of the Spinal Cord. 609 



of the annulosa, is proved by the experimental determination of the po- 

 sition for other centers, for actions of a considerable degree of com- 

 plexity. " After cutting the spinal cord above the lumbar enlargement, 

 Groltz and Freusberg found that very complicated functions are per- 

 formed through this lower nerve center, even when it is thus discon- 

 nected from the brain, and the animal, therefore, in a state of uncon- 

 sciousness. Nerves from this center reach the intestines, rectum, blad- 

 der and reproductive organs. The action of all these parts may be 

 carried on in a normal manner in dogs of both sexes, when mutilated 

 in the above manner, even to the production, by appropriate stimulation, 

 of sexual excitement and impregnation, followed in due time by normal 

 automatic parturition. On the other hand, the operation of all these 

 organs is summarily stopped, if this part of the spinal cord is destrc^ed, 

 even when all the rest of the nervous system and brain are intact. 

 When the brain of the animal is in normal connection with the spinal 

 cord, it is sometimes, but by no means always, the medium or route 

 through which the stimulus passes from the environment to the cord. 

 When it is disconnected, as in the case of the above experiments, the 

 stimulus applied by the operator to the motor roots and nerves, supplies 

 in some cases, that which the brain should furnish, and demonstrates 

 the purely mechanical nature of the entire apparatus. 



FIG. 347 .Transverse section 

 of spinal cord. Human embryo 

 at five months. ( From Ferrier.) 

 ah. Anterior horns of gray sub- 

 stance. 



ph. Posterior horns of gray sub- 

 stance. 



or. Root zones of efferent (or an- 

 terior) nerves.. 



pr. Root zones of posterior, or 

 (Coli 



afferent nerves. 

 Burdach ). 



lumns of 



jnr 



T- Columns of Turck. 



G Columns of Goll. 



dc. Tracts leading directly to 



the cerebellum. 

 p. Pyramidal fibres of lateral 



columns, 

 c. Commissure between the 



two halves of the spinal cord. 



As already mentioned, 

 FIG. 347. the nerves which reach the 



spinal cord from the various parts of the body do not all have the same 

 destination. Some, both afferent and efferent, end at the ganglia and 

 gray vesicular matter in the spinal cord where they first reach it. Others 

 continue up the cord and terminate in the medulla oblongata ; others go 

 on to the cerebellum ; and still others go to the optic thalamus without 

 break of connection. The figure ( 347 ) of a cross-section of the spinal 

 cord shows the position in the cord of some of these tracts. 



The general columns of gray matter in the spinal cord extend its 

 whole length, but the gray matter is more abundant at the points where 



