THE MUSCULAR FIBRE AND CONNECTIVE TISSUE OF THE UTERUS. 375 



3. Vessels and Blood-Corpuscles. 



In the earlier part of this paper I have alluded to the marked changes which occur in the vessels 

 during the latest stages of pregnancy, and also to the importance of the sinus-like character of the veins. 

 In the veins we find the following changes : — 



(1) An immediate compression of the sinus-like and smaller veins. 



(2) Many of these vessels later again become pervious ; but others remain permanently 

 compressed, their endothelial cells coming to present a hyaline and granular appearance, gradually 

 diminishing in volume, and finally disappearing. 



(3) In some of the veins a true process of proliferation of the intima goes on — this being started 

 at points where the neighbouring endothelial cells are brought into contact by the folding of the 

 vein wall on itself. 



In the arteries we find three varieties of change : — 



(1) Simple hyaline and granular change in the endothelial cells of the smaller arteries — many 

 of which come to be compressed in the same way as the veins. 



(2) In the somewhat larger vessels, there is during pregnancy a hyaline swelling of the mus- 

 cular and internal coats, both muscle cells and endothelium; this is followed by a gradual 

 diminution in volume — just as in the muscle cells of the uterine wall. Their lumen is blocked 

 from within by the swelling of the muscular coat and intima, instead of by compression from 

 without. These vessels also gradually disappear. 



(3) In the larger arteries a true process of proliferative endarteritis (as shown in fig. 10) 

 goes on. A rapid growth of cells takes place apparently from the endothelial cells and the sub- 

 endothelial connective tissue of the intima ; the growth being generally asymmetrical — one side 

 of the vessel wall growing more rapidly than the other, so that the lumen, instead of being circular, 

 comes to be crescentic. In many cases the lumen becomes completely blocked. At the same 

 time, the cells of the muscle coat become smaller, and probably eventually disappear. The lumen 

 comes to be represented by a fibrous cord, which in its turn is gradually absorbed. 



It may be well to point out again the fact that the plasmodia are especially congregated 

 round the vessels, and no doubt they assist in absorbing the contents of the cells of the vessels 

 which are undergoing the gradual diminution. 



What is the fate of the red blood-corpuscles which lie in the blocked vessels and in the extra- 

 vasations ? This is twofold : — 



(a) Many of the red corpuscles shrink and break up into a brownish granular mass — especially 

 those which have escaped into the surrounding tissues — owing to rupture of the vessel wall. 



(b) The second process is that of absorption by cells — either the whole corpuscle being 

 absorbed, or the above disintegrated fragments. Large clear endothelioid cells may be seen filled 

 with brownish-yellow granules, and here and there whole corpuscles with a complete circular out- 

 line. After absorption, the hsematin undergoes transformation into the brown pigment, the 

 corpuscles breaking up into minute granules. 



I think there can be no doubt that this transformation of the haematin can go on both within 

 and without the cells (phagocytes), because one sees — 



(1) "Whole corpuscles in the interior of cells. 



(2) Eed corps breaking down while still contained within the lumen of the vessel. 



Most of the phagocytes (which are especially numerous about the sixth day) wander off out of 

 the uterus with their load of pigmented granules ; others, however, appear to remain permanently, 

 for in the uterus which has once undergone the changes of the pregnancy and puerperium, there are 

 always to be found a certain number of these cells with brown-yellow contents. 



Taking then a general retrospect of the changes that occur in the uterus from the virgin con- 

 dition through pregnancy to the end of the puerperium, we may look upon the musculature as 

 the essential or specific element of the uterus with a supporting framework of connective tissue. 



VOL. XXXV. PART 8. 3 Q 



