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TEXT-BOOK OF PHYSIOLOGY. 



gland the lymphatics again emerge as efferent vessels to unite to form larger 

 trunks. A section of a gland shows that it consists of an outer dense cortical 

 and an inner soft pulpy medullary portion. Each gland is covered exter- 

 nally by a dense membrane of fibrous tissue containing in its meshes non- 

 striated muscle-fibers. From the inner surface of this membrane there pass 

 inward septa of connective tissue which, as they converge toward the center 

 of the gland, divide its outer zone into small conical compartments or 



alveoli. When the septa reach the medul- 

 lary portion, they subdivide and form 

 bands or cords which interlace in every 

 direction and constitute a loose meshwork 

 the spaces of which communicate with one 

 another and with the alveoli (Fig. 89). 

 Within the meshes of this framework the 

 proper gland substance is contained. In 

 the cortical compartments it is moulded 

 into pear-shaped masses; in the medullary 

 meshwork it assumes the form of rounded 

 cords which are connected with one another. 

 In both regions, however, it is separated 

 from the septa by a space termed a lymph 

 sinus, through which the lymph flows as it 

 passes through the gland. The lymph 

 sinus is crossed by a network of retiform 

 connective tissue which offers considerable 

 resistance to the passage of the lymph. 

 The gland substance consists also of a 

 framework of retiform connective tissue in 

 the meshes of which large numbers of 

 lymph-corpuscles are contained. The 

 gland substance is separated from the 

 lymph sinus by a dense layer of a reti- 

 culum, which, however, does not prevent 

 lymph and even corpuscles from passing 

 through it into the lymph sinus. 



The lymph-glands are abundantly sup- 

 plied with blood-vessels. The arteries enter 

 the gland at the hilum, penetrate into the 

 medullary substance, and terminate in a fine 

 capillary plexus which is supported by the 

 connective tissue. The veins arising from 

 this plexus leave the gland also at the 

 hilum. 



The lymph-vessels which enter a gland 

 first ramify in the investing membrane and 

 then open directly into the lymph sinus. The vessels which leave the gland 

 are also in communication with the sinus. After the lymphatics enter the 

 gland they lose their external and middle coats, retaining only the internal 

 or endothelial coat, which lines the inner surface of the lymph sinus. 



FIG. 88. LYMPH-VESSELS OF THE 

 ARM. (D caver.) 



