LYMPHATIC GLANDS. 121 



LESSON XXIV. 



LYMPHATIC GLANDS, TONSIL, THYMUS. 



1. SECTIONS of a lymphatic gland which has been stained in bulk and em- 

 bedded in paraffin. 1 Notice (1) the fibrous and muscular capsule, with 

 trabeculae extending inwards from it through the cortex and anastomosing 

 with one another in the medulla, (2) the dense lymphoid tissue (adenoid 

 tissue of some authors) forming large masses in the cortex (cortical nodules) 

 and rounded cords in the medulla (medullary cords). Notice also the clearer 

 channel or lymph-sinus which everywhere intervenes between the fibrous 

 tissue and the lymphoid tissue. Observe the fine fibres and branched cells 

 which bridge across this channel. 



Make a general sketch under a low power of a portion of the cortex 

 together with the adjoining part of the medulla, and under a high power 

 drawings of small portions of cortex and medulla. 



The retiform tissue of the lymphatic glands has already been studied 

 (Lesson IX.). 



2. In sections of tonsil prepared similarly to those of the lymphatic gland, 

 notice the large amount of lymphoid tissue only imperfectly collected into 

 nodules. Observe also that the stratified epithelium, which covers the mucous 

 membrane here as elsewhere in the mouth, is infiltrated with lymph- 

 corpuscles. Here and there pit-like recesses may be met with, and glands 

 opening into the pits. 



3. A similar preparation of the thymus gland of an infant. Notice that 

 the masses of lymphoid tissue which form the lobules of the gland are 

 separated by septa of connective tissue, and that they show a distinction into 

 two parts, cortical and medullary. Observe the differences of structure of 

 these two parts, and especially notice the concentric corpuscles in the medul- 

 lary part. 



Make a sketch of one of the lobules under a low power and of a small part 

 of the medulla under a high power, including one or two concentric corpuscles. 

 Measure the latter. 



Structure of a lymphatic gland. A lymphatic gland is composed 

 of a fibrous and muscular framework, which incloses and supports the 

 proper glandular substance, but is everywhere separated from it by a 

 narrow channel, bridged across by cells and fibres, which is known as 

 the lymph-channel. The framework consists of an envelope or capsule 

 (fig. 146, c), and of trabeculce (tr\ which pass at intervals inwards from 

 the capsule, and after traversing the cortex of the gland divide and 

 reunite with one another so as to form a network of fibrous bands. At 



1 See Appendix. 



