( '231 ) 



VIII. — A Contribution to the Comparative Anatomy of the Mammalian Organ of 

 Jacobson. By R. Broom, M.D., B.Sc. Communicated by Sir Wm. Turner. 

 (With Two Plates.) 



(Read 7th June 1897.) 



Since the Organ of Jacobson was first described in 1811, a large amount of study has 

 been given to its structure, development, and morphology ; and as a result of these 

 investigations, we have now a very good idea of the distribution of the organ in the 

 animal kingdom, of its relations in many typical forms, and of its minute anatomy in a 

 few representative types. With the exception, however, of Seydel's work among the 

 Amphibia, very little has been done to the study of the comparative anatomy of the 

 organ, and it is hoped that the present contribution will assist towards a clearer under- 

 standing of its comparative anatomy in the Mammalia. 



The organ is present in the large majority of mammals, and is generally fairly well 

 developed. The most important investigations into the general anatomy of the organ 

 and its relations have been those of Gratiolet, Balogh, Klein and Herzfeld. 

 Gratiolet has apparently examined the organ and its relations in a considerable 

 number of the higher mammals, but, unfortunately, I have been unable to see his paper. 

 Balogh has made a very careful study of the relations and minute anatomy of the 

 organ in the sheep, and has shown the complicated arrangement of the cartilages in 

 connection with the organ and its duct and with the naso-palatine canal. To Klein we 

 are indebted for a very careful study of the organ and its relations in the guinea-pig, 

 the rabbit and the dog. Though Herzfeld has also added considerably to our know- 

 ledge by the examination of some interesting new groups, his most important contri- 

 bution to the subject has been in connection with the comparative anatomy of the 

 organ. He has apparently been the first to recognise that, according to the various 

 relations of the organ and its duct found in different mammals, it was possible to 

 arrange the animals examined into a few not altogether unnatural groups. Owing to 

 observations having up to that time been made in an insufficient number of forms, he 

 has, unfortunately, over-estimated the importance of certain points, and thus to a large 

 extent has rendered his grouping unsatisfactory. 



The present communication deals with the results of an extended examination into 

 the general relations of the mammalian organ — its distribution, varying degree of 

 development, and extent of variation in allied forms. In all the forms I have studied, I 

 have made the examination by a series of vertical transverse sections, which seems the 

 most satisfactory method, and gives uniformity in the results. 



VOL. XXXIX. PART I. (NO. 8). 2 N 



