328 ON GROWTH AND OVERGROWTH 



cells, when they gain entrance into the maternal blood sinuses, 

 passing along the walls, digest and replace the endothelium of 

 those sinuses, so that eventually there is developed a most 

 complicated system of passages lined by cells of foetal origin and 

 containing maternal blood ; or almost, in the words of Matthias 

 Duval, the placenta is to be regarded as "a maternal haemorrhage 

 encysted by foetal tissue." By this remarkable " adaptation " 

 the foetus gains nourishment from the maternal blood. 



I have described this at some little detail because I wish to 

 impress upon you that here, as a normal or physiological con- 

 dition, we have passing those identical processes of invasion and 

 infiltration which we have been accustomed to regard as peculiar 

 to, nay, as the essential feature of malignant growth. The only 

 difference between what is here seen and malignancv is one of 

 degree, or perhaps, more correctly, of orderliness. This in- 

 filtration is due to the inherent properties of the syncytial cells. 

 Nor would this appear to be by any means the only case of 

 antagonistic " phagocytic ' cellular activity. Metchnikofr has 

 of late been engaged in collecting evidence to prove that such 

 activity is fairly general within the organism, and is the basis 

 of senile changes. 



Under ordinary conditions this syncytial invasion is strictly 

 limited ; it only affects a definite area of the uterine wall, and 

 with parturition and the separation of the placenta the whole 

 area of invasion is separated off and discharged. In other words, 

 to explain these normal phenomena (if the phrase be permissible), 

 we have to recognize the existence and interaction of two forces 

 — on the part of the foetal cells of invasive properties, on the part 

 of the maternal tissues of protective properties. 



Having laid this down, I may now approach my main point. 

 Occasionally — and apparently not so very occasionally, for 

 Marchand collected from the literature some sixty-five cases 

 recorded between the beginning of 1895 and the middle of 1898 — 

 these syncytial cells, after normal labour, are found to take on 

 aberrant growth, to trespass beyond the placental site, to infiltrate 

 extensively the uterine walls, the vaginal tissues, the pelvic 

 tissues in general, and, what is more, to form secondary growths 

 in distant organs, the lungs, the spleen, the brain, and so on. 

 These svncvtial cells are large and characteristic ; there is 

 nothing quite like them. We have, that is to say, as nearly 



