198 



COMPARATIVE. 



constricted off and modified part of the invaginated mucous membrane of the 

 pharynx and contains glandular ducts with clear or dark cells. The extract ob- 

 tained from the pituitary body contains iodin and causes an increase in the blood- 

 pressure, which, however, is less than that caused by an extract of suprarenal 

 gland; the heart-beat becomes slower and more forcible. 



The function of the coccygeal gland, which is situated at the extremity of the 

 coccyx, is unknown. 



The carotid gland, which occurs in man and mammals, and contains a con- 

 voluted plexus consisting of intricately anastomosing capillaries within an epithe- 

 lioid cellular mass, supported by a reticulum, has been compared by Stilling to 

 the suprarenal bodies. Its function is unknown. 



COMPARATIVE. 



The heart in fishes (Fig. 74, /) and in the gill-bearing larvae of amphibia is 

 a simple venous organ, consisting of auricle and ventricle. The latter sends the 

 blood to the gills, where it is arterialized, and passing to the aorta it is dis- 



I. 



FIG. 74. Diagrammatic Representation of the Circulation. 7. In Fish: A, auricle with the sinus venosus (5); 

 V, ventricle; B, bulb of the aorta-, c, branchial arteries; i i, branchial vessels; D, branchiales veins; E, circulus 

 cephalicus aortae; F, common aorta; G, caudal artery; H, ductus of Cuvier; /, anterior cardinal vein; K, 

 posterior cardinal vein; 7_, caudal vein; M M, kidneys. II. In the Frog: 7, sinus venosus; 77, right auricle; 

 777, left auricle; IV, ventricle; V, common trunk of the aorta and bulb, giving off the following: i, pulmonary 

 arteries; 2, arch of the aorta; 3, carotid arteries; 4, lingual arteries (5 carotid gland); 6, axillary arteries; 

 7, common aorta; 8, celiac artery; 9, cutaneous arteries; y, pulmonary veins; p p, lungs. 777. In Saurians: 

 7, right auricle with venae cavar, 77, right ventricle; 777, left auricle; IV, left ventricle; V, anterior common 

 aorta; i, pulmonary artery; 2, arch of the aorta; 3, carotid arteries; 4, posterior common aorta; 5, celiac 

 artery; 6, subclavian arteries; 7, pulmonary arteries; 8, lungs. IV. In Turtles: 7, right auricle with venae 

 cavae; 77, right ventricle; 777, left auricle; 7 F, left ventricle, i, right aorta; 2, left aorta; 3, posterior common 

 aorta; 4, celiac artery; 5, subclavian arteries; 6, carotid arteries; 7, pulmonary arteries; 8, pulmonary veins. 



tributed to all parts of the body, returning finally through the capillaries and 

 the veins to the auricle. The amphibia (frog, II) have two auricles and one ven- 

 tricle. From the latter there arises a single vessel, which, after giving off the 



