140 ALAN C. SUTTON 



will outweigh the appearance of high magnifications of neuro- 

 fibrils coated with a precipitation of silver. If an intermediate 

 substance stands between the passage of the impulse from nerve 

 to muscle in the one case, the chances are that a similar, though 

 most likely differently arranged, substance stands between muscle 

 and nerve in the other case. 



In order to see if this placque degenerated with the sensory 

 nerve, I performed a series of experiments upon rabbits. Fol- 

 lowing Huber's ('00) work upon the motor endings, I cut the 

 posterior tibial nerve of one leg and examined the plantar in- 

 terossei muscles after the nerves had degenerated. Using the 

 normal leg as a control, I was unable to stain anything that re- 

 sembled the placques after the nerve and nerve endings had de- 

 generated. This staining is not as satisfactory as a pharma- 

 cological test such as with curare and nicotine on the motor end 

 plates — and I am unwilling to draw any conclusions from a 

 negative finding one way or the other. It appears, however, that 

 whatever the nature of the placque, it loses its staining properties 

 with the degeneration of the nerve ending. 



Beyond this 175 mm. stage there is little more to describe 

 except the gradual growth in the size of the ending, which is al- 

 ready approximately identical with the adult spindle. Two 

 changes, however, are worth mentioning; the intricate plexus of 

 small nerves disappears gradually until we simph^ have the large 

 branching nerves which have now become medullated, running 

 here and there throughout the muscle. The other point is that 

 the intrafusal muscle fibers, which in the stages already de- 

 scribed are striated throughout their entire length, when they 

 get beyond the 200 mm. length begin to lose their striations 

 within the spindle sheath. At the 200 mm. stage the average 

 spindle consists of a heap of nuclei of both connective tissue and 

 muscle origin, in addition to the several muscle fibers with the 

 intricate annular and flower-spray endings. The entire mass is 

 enclosed in a connective tissue sheath, which becomes distinct at 

 about this stage of development. Some of the spindles include 

 as many as fifteen fibers. This is essentially the same picture 

 that we find in the adult eye muscles of the pig. 



