ABSORPTION. 



305 



rhythmical, occurring about sixty times in a minute, slowly, and, in 

 comparison with those of the blood-hearts, feebly. The pulsations of the 

 cervical pair are not always synchronous with/those of the pair in the 

 ischiatic region, and even the corresponding sacs of opposite sides are 

 not always synchronous in their action. 



Unlike the contractions of the blood-heart, those of the lymph-heart 

 appear to be directly dependent upon a certain limited portion of the 

 spinal cord. For Volkmann found that so long as the portion of spinal 

 cord corresponding to the third vertebra of the frog was uninjured, the 

 cervical pair of lymphatic hearts continued pulsating after all the rest 

 of the spinal cord and the brain were destroyed; while destruction of 

 this portion, even though all other parts of the nervous centres were un- 

 injured, instantly arrested the heart's movements. The posterior, or 

 ischiatic, pair of lymph-hearts were found to be governed, in like man- 

 ner, by the portion of spinal cord corresponding to the eighth vertebra. 

 Division of the posterior spinal roots did not arrest the movements; but 

 division of the anterior roots caused them to cease at once. 



Lymphatic Glands. 



Lymphatic glands are small round or oval compact bodies varying in 

 size from a hempseed to a bean, interposed in the course of lymphatic 



FIG. 221. 



FIG. 222. 



FIG. 221. Section of a mesenteric gland from the ox, slightly magnified, o, Hilus; 6 (in the cen- 

 tral part of the figure), medullary substance; c, cortical substance with indistinct alveoli; d, cap- 

 sule (Kolliker.) 



FIG. 222. Section of medullary substance of an inguinal gland of an ox; a, a, glandular sub- 

 stance or pulp forming rounded cords joining in a continuous net (dark in the figure) ; c, c, trabec- 

 ulae; the space, 6, 6, between these and the glandular substance is the lymph sinus, washed clear of 

 corpuscles and traversed by filaments of retif orm connective tissue. X 90. (Kolliker.) 



vessels, and through which the chief part of the lymph passes in its 

 course to be discharged into the blood-vessels. They are found in great 

 numbers in the mesentery, and along the great vessels of the abdomen, 

 thorax, and neck; in the axilla and groin; a few in the popliteal space, 

 but not further down the leg, and in the arm as far as the elbow. Some 



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