98 THE FROG CHAP. 



eating with the subclavian, the posterior with the renal portal 

 vein. 



The lymphatics of the enteric canal have an important function to 

 perform in that they absorb the fatty portions of the food (p. 75). The 

 fluid they contain has a milky appearance, owing to the presence of 

 minute suspended fat-globules, and for this reason they receive the name 

 of lacteals. 



The ccelome is really a great lymph-sinus. It communi- 

 cates with the veins of the kidneys through certain micro- 

 scopic apertures called nephrostomes (nst) (Fig. 23, ccel). 



The spleen (p. 23, and Fig. 3, spt) has important relations 

 with the blood- and lymph-vessels, and probably acts as a 

 blood-filter, removing particles in the blood which are no 

 longer wanted. 



PRACTICAL DIRECTIONS. 

 The Vascular System. 



a. Let some blood from a frog or better from the veins of some larger, 

 freshly-killed, warm-blooded animal, such as a rat or a rabbit flow 

 directly into a white cup or porcelain capsule. Note that it soon 

 coagulates i and soon afterwards separates into clot and serum. Notice 

 also the difference in colour between the blood freshly drawn from a 

 vein (cf. p. 85), and that soon assumed by exposed portions of the clot. 



b. Pin a freshly killed frog to the dissecting board, dorsal side 

 upwards, and cut through the skin of the back along the middle line. 

 The posterior lymph-hearts (p. 97, Fig. 23) will then be seen. To make 

 out the anterior lymph-hearts, carefully separate the supra-scapuloe from 

 the vertebral column. Some of the chief lymph-sinuses have already 

 been seen : special methods are required to trace the lymph-vessels. 



c. Now turn the frog the other way upwards, pin it down in the dissect- 

 ing dish, and open the body-cavity as before (p. 32), taking great care 

 not to cut the abdominal, musculo-cutaneous, and other veins. Slit open 

 the pericardium and remove as much of it as possible, so as to 

 expose the entire heart. The structure of the heart and the course of 

 many of the blood-vessels can also be made out in the specimen from 



