8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 72 



TANGENTIAL SECTION OF THE FEMUR OF A PRAIRIE CHICKEN, 



TYMPANUCHUS AMERICANUS, SHOWING THE 



CIRCULATION 



Pl. 2. Fig. 14 



The type of bone is first. A few entering vascular canals, without 

 surrounding lamellae, are seen in the bone substance. The circula- 

 tion is a rich plexus of blood vessels with small, round and irregularly 

 shaped meshes. It is situated nearer the periosteal than the medullary 

 surface. The lacunae of the bone substance are round or oval and 

 have short bushy canaliculi. 



TANGENTIAL SECTION OF THE FEMUR OF A DOMESTIC DUCK, 

 ANAS DOMESTICA, SHOWING THE CIRCULATION 



Pl. 2, Fig. 15 



The type of bone is an early second. The section has two rich 

 plexuses of blood vessels, one above the other, with bone substance 

 between them. The meshes are quite regular in form and somewhat 

 larger than those found in the other birds examined. Here and there 

 are seen entering vascular canals without surrounding lamellae. The 

 lacunae of the bone substance are round or oval with short bushy 

 canaliculi. 



CROSS AND TANGENTIAL SECTIONS OF THE FEMUR OF A 

 FRUIT BAT, PTEROPUS (CELEBES) 



CROSS SECTION SHOWING THE STRUCTURE 



Pl. 2, Fig. 16 



The section is composed of a wide central ring of lamellae per- 

 forated in the inner wall by a few vascular canals extending length- 

 wise of the bone. Internal circumferential lamellae surround the 

 medullary canal and poorly differentiated external lamellae surround 

 the section. The lacunae are oval with straight canaliculi. 



TANGENTIAL SECTION OF THE SAME FEMUR SHOWING THE 

 CIRCULATION 



Pl. 2, Fig. 17 



In this section are seen the vascular canals of the inner wall extend- 

 ing from above downward and inward. The canals are parallel with 

 each other and some of them are branched. They were absent in the 

 outer wall. 



