ON" THE FATE OF THE MUSCLE-PLATE, AND THE 

 DEVELOPMENT OF THE SPINAL NERVES AND 

 LIMB PLEXUSES IN BIKDS AND MAMMALS. 



By A. M. Paterson, M.D., 



Senior Demonstrator of Anatomy, and Lecturer in Dental Anatomy 

 and Physiology, in the Owens College, Manchester. 



[With Plates VII. and V1IL] 



The late Professor Balfour* showed that the spinal nerves in 

 Elasmobranchs spring entirely from epiblastic origins, and the same 

 has been proved conclusively regarding the roots at least of the 

 spinal nerves in birds and mammals, by the researches of Milnes 

 Marshall,! His, J and others. The most complete account of the 

 early stages in the development of the nerves in higher Vertebrates 

 is that of Marshall. He has traced the roots of the nerves from 

 their origin from the spinal cord to the point when they unite 

 together to form the mixed nerve. From that point onwards there 

 is uncertainty. Though it is considered highly probable that the 

 further growth of the nerves consists of an extension towards 

 the periphery of the original epiblastic elements, still it has not 

 been proved that this is so. It has not hitherto been shown that 

 the nerve-trunks, after the junction of the two roots, are not formed 

 from the cells of the mesoblast. 



The present investigation has been undertaken with the object of 

 tracing the nerves in their development from the condition in which 



* "Monograph on the Development of Elasmobrancb Fishes," London, 1878. 

 t "Journal of Anatomy and Physiology," vol. xi., p. 491. 



I "\'i}><r d. Anfango d. I'eriplicrischen Nerven .Systems," "Archiv f. Anat. u. 

 Pliys.," 1879. 



