no. 3 comparative histology of femur foote 17 



Frequency of Occurrence 



The distribution of the three types of bone, their stages of development, 

 and divisions may be seen in the following table: 



DISTRIBUTION OF THE THREE BONE TYPES AND THEIR DIFFERENTIATIONS 



Type 





Amphib- 

 ians 



Reptiles 



Birds 



Bats 



Other 

 mum' Is 



A u u 1 1 

 man 



r etal 

 man 



Total 





Number of femora examined.. . 



39 



34 



40 



55 



133 



139 



7 



440 









Per ccn t 



Pnn /.art* 



Per cent 



Per cent 



Per cent 



Per cent 



Per cen t 



I. 



Lamellae, uniform throughout. . 



26 



60 



30 



73 



0 



0 



0 



19 







r>i 



17 



7.5 



16 



2 



0 



0 



14 





Lamellae, threefold division.... 



20 



6 



5 



9 



0 



0 



0 



4 





Lamellae as cancellous bone. .. . 



3 



17 



5 



0 



46 



92 



100 



46 





Lamellae as important bone 























100 



100 



47 



100 



48 



92 



100 



79 



II. 



Laminae, incomplete differen- 





















tiation 



5 



9 



25 



0 



10 



0 



100 



18 





Laminae, complete differentia- 























0 



0 



0 



0 



40 



8 



0 



1.4 





Laminae as important bone 























5 



9 



25 



0 



50 



8 



100 



21 



III. 



Haversian system, fa 



21 



21 



5 



5 



39 



32 



14 



27 







0 



23 



7 



7 



28 



6 



71 



15 





Haversian svstem, Ic 



0 



0 



82 



0 



0 



0 



0 



7 





Haversian svstem, C 



0 



0 



0 



0 



82 



100 



0 



54 





Haversian system, incomplete 























21 



52 



89 



12 



67 



38 



18 



46 





Haversian system, complete 





















differentiation 



0 



0 



0 



0 



82 



100 



0 



54 



Looking over the above table it will be noticed that lamellae, in some stage 

 of differentiation, form an important part of the majority of all femora, and, 

 therefore, may be considered as the simplest, oldest, and most universal bone 

 units; that the first type of bone, without concentric divisions, has a wider 

 range than it lias with concentric divisions, and that cancellous bone — which is 

 first type with a special arrangement of lamellae — is found in all classes of 

 animals; that laminae — incomplete or complete — are found in the smallest num- 

 ber of femora, and that Haversian systems, in some stages of differentiation, 

 are found in the largest number of femora and to the greatest extent in man. 

 The early differentiations of the Haversian systems are found in 4(i% and the 

 late in 54% of all femora examined. There are more early differentiations in 

 the lower animals and more late differentiations in man than in the lower 

 animals. Early and late differentiations may occur in the same bone and more 

 especially in mammals and man, as may be seen in such femora as represented 

 in plate 31, figure 399. 



two laminae occurred at intervals. Around these enlargements two to four concentric lamellae were 

 arranged, the whole figure presenting the appearance of a small Haversian system (pi. A, fig. P). 

 These are referred to in the detailed description as aberrant forms of the Haversian system. 



