Wyman.] 268 [June 5, 



of the radius and iJna." " The upper third of the fibula is repre- 

 sented by the anterior or coronoidal part of the ulna." " In all mam- 

 mals the two lower thirds of the tibia represent the corresponding part 

 of the radius, and the two lower thirds of the fibula that of the ulna." * 



The view of Prof. Owen is as follows : " The skeleton of the 

 Phalangista or Phascolomys plainly demonstrates that the tibia is the 

 homotype of the radius, and that the fibula is the homotype of the 

 ulna."f The same conclusions are adopted by Humphrey. 



Thus putting together the views of the anatomists above cited, we 

 have: 



1st. The ulna = the tibia of the opposite side. 



2d. The ulna = the tibia of the same side. 



3d. The ulna = the fibula. 



4th. The head of the tibia = the heads of the radius and ulna. 



The fibula = the coronoidal and lower two-thirds of the ulna. 

 The lower two-thirds of the tibia = the corresponding part 

 of the radius. 



5th. The tibia = the upper half of the ulna and the lower half 

 of the radius. 



The fibula = the upper half of the radius and the lower half 

 of the ulna. 



There seems to be no sufficient reason for entering into a discussion 

 of the views of those who consider a bone of one limb homologous with 

 parts of two different bones in another. We do not know of any 

 unquestioned analogy in the whole range of comparative anatomy 

 which can be brought forward in support of it. 



Prof. Owen sustains his opinion, already cited, by the following 

 statement, and in this he is followed by Humphrey and others : "In the 

 Wombat the part of the fibula representing the olecranon is a de- 

 tached sesamoid, as the olecranon itself is in the penguin and the bat. 

 In the Ornithorhynchus the fibula (Fig. 14, B) assumes the proportions 

 and develops the process from its proximal end, the want of which 

 in man and most mammals, deceived Vicq d'Azyr as it misled, more 

 recently, M. Cruveilhier." 



We are somewhat at a loss to know what is to be understood by the 

 expression " detached sesamoid," inasmuch as a sesamoid, as commonly 

 understood by anatomists, is always detached. The only interpreta- 

 tion which suggests itself to us is, that it is used synonomously with 

 an epiphysis, and that the bone connected with the upper end of the 

 fibula in the Wombat is the detached epiphysis of that bone, and this 

 he considers homologous with the large process on the upper end of 



* Mem. Acad. Sciences. Montpellier, T. iii, p. 536. 



t Archetype and Homologies of the Vertebrate Skeleton. London, 1848, p. 167. 



