I.. I.] THE FROG. 131 



S. 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 lamella : cf. supra. 



ft. 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 lacunas 

 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 lamella?. 



i.. 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. 



9 — 2 



