374 MR T. ARTHUR HELME ON HISTOLOGICAL OBSERVATIONS ON 



corpuscles. Their function is evidently to eat up and carry off the blood-pigment. They are 

 especially numerous at the 10th day in the sub-epithelial connective tissue. After this time they 

 diminish greatly in number, probably wandering off, but representatives are to be found months 

 later. 



The Giant Cells. 



But of paramount importance and interest are those large multinuclear cells, which I have 

 found in the full-time uterus, and described as plasmodia. These cells are present only during the 

 last few days of pregnancy and the first days of the puerperium. What is their life-history ? 



Since the time when Haeckel first demonstrated the ingestion of colouring matter by the blood- 

 corpuscles of various invertebrates, numerous researches have followed, showing that this is a 

 property common to the wandering mesoderm cells, not only of invertebrates, but also of vertebrates, 

 including man. Metschnikoff and many others have shown that these cells are capable of not 

 only taking up foreign bodies introduced from without, but also resorbing structures that have no 

 further use, e.g., in the atrophy of larval tissues during metamorphosis. 



Further, Metschnikoff has shown that these cells have the power of coming together and fusing 

 to form one common mass or plasmodium, and that the so-called giant cells, so often found lying 

 round foreign bodies, have " in all cases (in invertebrates) arisen by fusion of separate cells." 



Geddes and others have observed that even outside the body, and loitlwut the presence of foreign 

 bodies, these cells have a great tendency to form plasmodia. 



Further, to quote Metschnikoff's own words — " In higher forms the mesoderm does not lose 

 its primitive powers, but employs them against useless and harmful bodies, so that it retains the 

 intracellular digestion, as well as many other of the characters of the protozoa — not only the power 

 of throwing out pseudopodia, but also that of forming plasmodia. Mesodermal plasmodia are found 

 even in the higher animals, not excepting man himself.""* 



Now it seems to me that here we have the explanation of what occurs in the rabbit's uterus. 



During the last days of pregnancy large clear cells with a single large nucleus appear in 

 numbers (derived most probably from leucocytes) ; these coalesce and form the multinuclear cells — 

 the plasmodia — so that by the end of pregnancy there is developed a large army ready for service. 

 Immediately the uterus has emptied itself of its contents, and its greatly increased tissues 

 completed their function, the plasmodia begin their work. They are no longer found lying in 

 groups, but are scattered and their protoplasm becomes progressively more granular. Evidently 

 their function is to eat up the waste material lying around them — whether in the form of granules 

 from the connective tissue, or in solution from the muscle cells. 



The process might be compared to some extent with the resorption of cartilage by 

 chondroclasts. 



In the developing bone we find a temporary framework of calcified cartilage, which is gradually 

 eaten up by the chondroclasts, to make way for the permanent bone. 



In the uterus we find a somewhat analogous process. In the developing uterus of pregnancy 

 we find a temporary framework of connective tissue developed to support the enlarged muscle cells, 

 and to convey the greatly augmented capillary vessels for their nourishment. In the puerperal 

 uterus this framework is no longer required, accordingly it is removed, and it is in this process that 

 the plasmodia seem especially to be concerned. 



It may be well here to recall the fact, that other uninuclear wandering cells (phagocytes) 

 assume the duty of ingesting the red blood-corpuscles, which lie in numbers in the blocked capillary 

 vessels. 



As to the destiny of the plasmodia, after taking in their load they wander off from the uterus (none 

 are to be seen on the 6th day post partum), and probably find their way into the general circulation 

 — whether as plasmodia or after breaking up again into their original elements is not evident. 



* " Researches on the Intracellular Digestion of Invertebrates," by Dr Elias Metschnikoff, Quart. Jour. Micr. Sci., 

 1884, vol. xxiv. p. 109. 



