332 



degenerated remains of a sheet of muscular tissue which has become 

 fibrous from alteration in the requirements of the limb into which it 

 is inserted, and the variations described above point to its being a 

 degenerated portion of the teres minor. 



Another suggestion which arises from these observations is that 

 the deltoid and the teres minor are derivatives of the same muscle 

 sheet. The hinder fibres of the deltoid usually pass downwards for 

 some distance from the spine of the scapula and obtain origin from 

 the fascia infraspinata, and the deltoid may even obtain separate 

 bands from this fascia. In the first case described the hinder fibres 



of the deltoid blended with the muscular tissue over the infraspinous 

 fossa. 



This hypothesis is supported by the similarity in the nerve supply 

 of the teres minor and deltoid, and it throws light upon the reason 

 for the large size of the nerve to the teres minor. 



A muscle which has phylogenetically become smaller retains its 

 original nerve supply undiminished in size for a long period after the 

 disappearance of the functionating portion, and the large size of the 

 nerve to the teres minor is explained by this hypothesis, that the 

 muscle originally occupied the whole surface of the infraspinous fossa, 

 and that the inner portion of it has become fibrous and is represented 

 by the fascia infraspinata. 



Embryology does not throw much light upon this matter, but the 

 available evidence is not opposed to the view which I have outlined, 



