40 PHYSIOLOGIC AI, 



A. 184. The exterior section of the same boues. The vessels 

 in the cartilaginous extremity are particularly distinct. 

 0. C. 156. Huntenan. 



A. 185. A metatarsal cartilage of a Calf, injected. The arteries 

 in several parts are of a whitish colour, from a deposit of 

 calcareous earth. 0. C. 138. Hunterian. 



A. 186. A section of the foot of a mature Human Foetus, injected, 

 showing the cartilaginous condition of the bones of the 

 tarsus, with the commencement of ossification in the os 

 calcis and astragalus. 0. 0. 133 D. 



A. 187. Section of the foot of a Boy 12 years of age, showing 

 the epiphyses of the lower part of the tibia, os calcis, 

 metatarsal and phalangeal bones, injected. The section 

 is through the middle of the first metatarsal bone. 

 0. C. 133 D a. Presented by J. Hilton, Esy. 



BONES CONTAINING GAS OR AIR. 



A. 188. Greater part of the crania of two Herrings (Clupea 

 harenyu^i), showing their ventral surfaces. In A the sur- 

 face has been left entire ; in B some bone has been removed 

 to show the three bony chambers on either side that lodge 

 an extension of the swim-bladder. Into the anterior of 

 these chambers extends a process of the membranous laby- 

 rinth. On the right side of B the chambers have been 

 opened, and have bristles passed into them. A portion of 

 the anterior extremity of the swim-bladder has been 

 retained and painted black. These gas-filled cavities 

 probably serve as resonating chambers subservient to 

 hearing. 



Ridewood, J. of Anat. & Physiol., vol. xxvi. 18i2, p. 2(i. 



A. 189. Posterior portion of the skull of a Crocodile (Crocodilus 

 acutus), with part of left ramus of the lower jaw attached. 

 A piece of the skull has been removed to show the interior 

 of the tympanic cavities which freely communicate with 

 one another above the brain-case. This may perhaps serve 



