529 



articulation. In agreement with Gillette, he arrived at the conclusion 

 that they are real periarticular components of the skeleton, and not of 

 fortuitous occurrence. 



Prior to 1885, the sesamoids of mammals other than Man had 

 received little notice. In this year appeared an elaborate and ex- 

 ceedingly valuable account of the development of the skeleton of the 

 mammalian extremities from the pen of Retterer i) ; and a section of 

 the paper was devoted to the consideration of the sesamoids, both 

 metacarpo-phalangeal and inter-phalangeal. Concerning the animals 

 with which the present communication deals, Retterer makes rather 

 brief mention ; and does not consider in detail the development of the 

 inter-phalangeal sesamoid. In a pig embryo, 7 cm long, he found the 

 metacarpo-phalangeal sesamoids in the third and fourth digits only. 

 The inter-phalangeal sesamoids were not discovered in any of the digits. 

 An embryo 15 cm in length had all the sesamoids; and at the time of 

 birth, they were vascular. In a rabbit embryo 6 cm long Retterer 

 apparently did not find any inter-phalangeal sesamoids ; though the 

 metacarpo-phalangeal ossicles are stated to be represented by carti- 

 laginous nodules. At the time of birth inter-phalangeal sesamoids were 

 present as masses of cartilage. At eighteen days after birth, these 

 were vascular ; and at the age of 34 days almost the whole of the car- 

 tilage was replaced by bone. 



Naturally, the most detailed accounts of the sesamoids of ungulates 

 are given in those treatises in which the skeleton of the domestic ani- 

 mals are described. But the authors of such works do not discuss the 

 development or significance of these bones. Indeed, the majority of 

 writers on veterinary anatomy leave it to be assumed that they are of 

 opinion that the inter-phalangeal sesamoid is developmentally very in- 

 timately associated with the tendon of the deep flexor muscle. For 

 example, Martin 2) and Ellenberger and Baum^) speak of it as "das 

 dritte Sehnenbein" ; but, it must be added, there is no direct statement 

 that the sesamoid developes within the tendon. 



It is evident from what has been said above that the early history 

 of the inter-phalangeal sesamoid bone has not been so fully described 

 as might be desired. Therefore, with the intention of discovering the 

 precise embryological relationship of the bone to the tendon, and the 

 mode of its earliest appearance, an examination has been made of the 

 manus of embryos of certain ungulates. Ungulates were made the 

 basis of the investigation because, in these animals, the sesamoid con- 



1) Retterer, Developpement du squelette des extremites et des 

 productions cornees chez les mammiferes. These pr^s. ä la Faculte des 

 Sciences de Paris, 1885. 



2) Martin, Lehrbuch der Anatomie der Haustiere. Stuttgart 1902. 



3) Ellenberger und Baum, Handbuch der vergleichenden Anatomie 

 der Haustiere. 10. Aufl. Berlin 1903. 



Anat. Anz. XXVIII. Aufsätze. 34 



