xi PRACTICAL DIRECTIONS 557 



capsule, and note the synovial membrane 2^^ fluid and the cartilaginous 

 articular stirfaces of the glenoid cavity and head of the humerus 

 respectively : or, prepare as directed on p. 64 in the case of the hip- 

 joint of the frog. 



4. As an example of a muscle with a multiple insertion, dissect out 

 the extensor communis digitorum (dorsal). It arises from the distal 

 end of the humerus, and at the distal end of the fore-arm divides into 

 four tendons, which pass through the annular ligament to digits 2-5 

 and are inserted on the middle and distal phalanges. Note the 

 sesamoid bones on the palmar side of the joints of the digits. 



J. Side dissection, 



Obtain another rabbit, and make a dissection from the side (compare 

 Fig. 135) as directed in the case of the dogfish and frog (p. 481). 

 Make out the structure and relations of all the principal organs once 

 more, and sketch your dissection. 



K. Transverse sections. 



The examination of transverse sections is most easily and satisfactorily 

 done by preparing microscopical sections of a foetus not more than 

 a couple of inches in length, as directed in the case of the young 

 dogfish (p. 480) : a foetal rat or mouse will answer the purpose equally 

 well. 



With a sharp knife, cut transverse sections, about Jth inch thick, from 

 the following regions : #, snout ; $, cranial region ; c , neck ; d, thorax ; 

 and e, abdomen. Stain and imbed, and then cut and mount one or 

 two sections of each, examining them with a low power and making 

 sketches. 



Then put on the high power, and make out as much as possible of 

 the histology of the various organs. 



[For the blood-corpuscles, examine a drop of blood obtained from a 

 freshly-killed rabbit or by pricking the tip of your finger (compare 

 p. 121). Note the circular and slightly biconcave form of the red 

 corpuscles, their relatively small size (about -g-vjVtf in. or *oo8 mm. in 

 diameter), and the absence of a nucleus.] 



