THE DEVELOPMENT OF THE HYPOGLOSSAL GANGLIA 

 OF PIG EMBRYOS 



C. W. PRENTISS 



Northwestern University Medical School 



EIGHT FIGURES 



The use of dissected pig embryos for classwork in embryology 

 suggested itself to the writer some years ago. Upon trial it was 

 found that very instructive preparations could be made and with 

 much greater ease than might be expected. It is difficult for stu- 

 dents to grasp the relations of developing organs as seen in sections 

 and a dissected embryo showing the primitive organs in position 

 is very helpful in remedying this evil. It is the intention of the 

 author to present, in a future paper, the results of his work along 

 these lines, with directions for dissection and figures of the more 

 instructive preparations. The form and relations of the various 

 organs may be seen as accurately as in reconstructions made from 

 serial sections by experts. There is this disadvantage in dissec- 

 tion, that some of the finer details of structure may be lost. For 

 research it commends itself as a check to errors which may occur 

 in making reconstructions; for it enables one in a short time to 

 study a considerable number of embryos. 



The nervous system lends itself most easily to dissection. The 

 mesenchyma crumbles away from the more tenuous nervous tissue 

 of suitably prepared embryos, making it possible to lay bare the 

 entire nervous system of pigs varying in length from 6 to 20 mm. 

 The smaller embryos are more easily dissected, as no cartilage 

 or bone is encountered. 



My dissections brought out some points in connection with the 

 cerebral nerves which have not hitherto been cleared up, and my 



THE JOURNAL OF COMPARATIVE NEUROLOGY AND PSYCHOLOGY, VOL. 20, NO. 4. 



