159 



LESSON XXXII. 



STRUCTURE OF THE SPLEEN, SUPRARENAL CAPSULE, AND 

 THYROID BODY. 



1. SECTIONS of the spleen stained with logwood. Notice the trabeculie extend- 

 ing into the substance of the organ from the capsule. Notice also that the 

 glandular substance is of two kinds, (1) lymphoid tissue accumulated round 

 the small arteries and here and there massed to form lymphoid nodules the 

 Malpighian corpuscles of the spleen and, (2) a tissue consisting of a 

 reticulum of branched and flattened cells containing blood in its interstices 

 and pervaded by capillaries and venous radicles. 



Sketch part of a section under a low power and a small portion of the 

 reticulum under a high power. 



2. Sections across a suprarenal capsule. Examine first with a low 

 power, noticing the general arrangement and extent of the cortical and 

 medullary parts of the organ, making a general sketch which shall include 

 both. Afterwards sketch carefully under the high power a group of cells 

 from each part of the organ. 



3. Sections of the thyroid body stained with logwood. Notice the vesicles 

 lined with cubical epithelium and filled with a ' colloid ' substance which be- 

 comes stained by the logwood. Notice also in some parts of the sections a 

 peculiar highly vascular retiform tissue. Sketch a part of this tissue and also 

 one or two vesicles. Measure several vesicles. 



THE SPLEEN. 



The spleen is the largest of the so-called ductless glands. It 

 appears to be connected in some way with the elaboration of the blood, 

 white blood-corpuscles being certainly formed and the coloured blood- 

 corpuscles being probably submitted to destruction within it. 



Like the lymphatic glands, the spleen is invested with a fibrous and 

 muscular capsule (fig. 193, A), and this again has a covering derived 

 from the serous membrane. The capsule sends fibrous bands or tra- 

 beculae (b) into the organ, and these join with a network of similar 

 trabeculae which pass into the gland at the hilus along with the blood- 

 vessels. In the interstices of the fibrous framework thus constituted 

 lies a soft pulpy substance containing a large amount of blood, and 

 therefore of a deep red colour, dotted within which are here and there 

 to be seen small whitish specks, the Malpighian corpuscles of the spleen 

 (c, c}. These are composed of lymphoid tissue which is gathered up 

 into masses which surround the smaller arteries, whilst the red pulp 

 which everywhere surrounds them and which forms the bulk of the 



