32 SMITHSONIAJT CONTRIBUTIONS TO KNOWLEDGE VOL. 35 



IV. HISTOLOGICAL EXAMINATION OF TWO ENTIRE HUMAN 

 FEMORA— GENERAL DESCRIPTION 



As all of the sections were made through the middle of the shaft, and the 

 descriptions given applied only to the structure of one location, it was desirable 

 to examine sections of entire femora of different types in order to determine 

 to wliat extent the structure of the middle of the shaft represented the whole 

 femur. "With this object in A'iew, two entire femora have been examined. In 

 each hone the first section was made transversely through the middle of the 

 head, and the remaining sections at intervals of 2.5 cm. The two femora 

 represented two types of differentiation — one, I-III, C, senile, and the other, 

 III, C, senile. 



The first femur (length 41 cm., No. 300, Cr. Med. Coll.).— Tliis was com- 

 posed of a predominating proportion of lamella; interrupted by Haversian sys- 

 tems of the (la) and (C) differentiation, enclosing a narrow ring of Haversian 

 systems of the (C) differentiation, many of which were senile. This femur, 

 therefore, represented a human bone with incomplete development. 



The structural type remained the same throughout the entire femur, but 

 the different sections showed variations in medullary indices, proportions of 

 lamella;, cancellous bone, and senile changes. The medullary indices diminished 

 from the extremities of the medullary canal toward the middle of the shaft, 

 and were lowest 15 to 20 cm. below the section of the head. 



The proportion of the lamella; to the enclosed Haversian systems increased 

 gradually from the head to the lower extremity. The cancellous bone dimin- 

 ished from the extremities toward the middle of the shaft. The senile changes 

 were most numerous in the middle of the shaft and in the anterior wall. 



On the whole, the bone was composed of an external, thick sheath of lamellfe 

 enclosing a thin, shorter sheath of Haversian systems, and a section through 

 the middle of the shaft gave a fair representation of the whole bone structure, 

 excepting that of the two extreniities. 



It was noticed during the grinding of the middle sections that the lamellar 

 and Haversian system rings were easily separated from one another, and that 

 they were readily fractured in the anterior wall in which senility was most 

 marked. 



Second femur (length 38 cm.. No. 301, Cr. Med. Coll.). — The upper portion 

 of this femur was composed almost entirely of well developed Haversian sys- 

 tems and the lower portion of lamellfE and Haversian systems. The lamella^ 

 formed a wide exlei'nal band situated in the anterior wall, and were fre(|ueiitly 

 interruiitcd by Haversian systems, some of which were senile. 



The lidiu' i-epresented a human femur of a much later differentiation tliaii 

 No. 300, although it was not entirely a i)uro third type i)one. The pi-incipal 

 \ai-iation from llic third type was limited to the lower portion. 



