I.] THE FROG. 131 



8. The marrow ; note the aggregation of small 

 cells on the inner face of the shaft. 



d. Make a transverse section of the dried shaft of the 

 femur, by grinding it down upon a hone as di- 

 rected in the Appendix (E.). Mount in Canada 

 balsam and examine under a high power, 

 a. The lamelltz : cf. supra. 



(3. The lacuna; oval spots between the lamellae; 

 black, as they become filled with dirt in grind- 

 ing. Each originally lodged a bone-corpuscle. 



y. The canaliculi; minute black lines radiating 

 from the lacunae. Those of adjacent lacunae 

 frequently anastomose. 



8. The Haversian canals; present only in the 

 neighbourhood of the nutritive foramina. Ob- 

 vious as spaces in the substance of the shaft, 

 each surrounded with its own lamellae. 



e. Examine a longitudinal section of the dried 

 femur, for comparison with the above. The 

 'Haversian canals are seen to be channels run- 

 ning for the most part longitudinally, and com- 

 municating with one another by cross branches. 

 The lacuna and canaliculi appear much as in 

 the transverse section. 



The study of the dried bone may advanta- 

 geously be supplemented by that of the long 

 bone of a mammal. 



6. Adipose tissue. 



Tease up portions of the corpus adiposum, as under. 



a. Fresh, in salt solution. Examine under a low 

 power ; the following will be met with. 



92 



