DEPARTMENT OF EMBRYOLOGY. 121 



cases the patients died without aborting. This would indicate that 

 when the ovum and the placentation are normal it requires an extremely 

 severe disturbance in the condition of the mother to bring about the 

 termination of pregnancy. 



As regards the course and prognosis of influenza in pregnant women, 

 it was found that about one-half of all the patients developed pneu- 

 monia, and of these about 50 per cent died, giving a gross mortality of 

 27 per cent. In those developing pneumonia the mortality was some- 

 what higher in the last 3 months of pregnancy, reaching its highest 

 point (61 per cent) in the last month. Where the disease is compli- 

 cated by abortion or premature labor the prognosis appears to be more 

 grave. In 383 cases of pneumonia in which pregnancy was not inter- 

 rupted, the mortality was 41 per cent, whereas in 395 cases in which 

 it was interrupted there was a mortality of 63 per cent. 



Professor A. W. Meyer has made a special study of double-ovum 

 twins in which the two embryos present marked differences in size and 

 development. He found four specimens of this character in the Carnegie 

 Collection, and his examination shows that in each case one twin died 

 and was retained until the birth of the other, which resulted in a con- 

 siderable difference in their apparent ages. The discrepancies in size 

 ran as follows: No. 587 {a) empty chorion, (6) cyhndrical embryo 7 

 mm.; No. 788 (a) stunted embryo 17 mm., (6) nodular embryo 3 mm.; 

 No. 1840 (a) normal embryo 31 mjn., (6) normal embryo 15 mm.; No. 

 2036 (a) normal embryo 87 mm., (6) macerated embryo 23 mm. Simi- 

 lar discrepancies in the size of the chorions may or may not occur. 



It is clear that such cases might easily be classed with the alleged 

 instances of superfetation found in the literature, although undoubtedly 

 it would be a misinterpretation of the facts. Dr. Meyer points out 

 that it is such cases of twin pregnancy that are responsible for the 

 prevalent belief in the occurrence of superfetation in v/omen, for the 

 existence of which he finds no real evidence. 



In addition to the light which it throws upon superfetation, the 

 preceding paper is of importance in connection with the question of 

 retention of the chorion after the death of the embryo, and Dr. Meyer 

 has extended his studies to the consideration of this subject. Although 

 there is abundant evidence of the phenomenon of retrogression and 

 partial as well as total intrauterine absorption of the conceptus in 

 several of the mammals, the literature has thus far shown no conclu- 

 sive evidence regarding its occurrence in man. Marked maceration, 

 putrefaction, and dissolution of the human fetus are well known, but 

 cases of intrauterine autolysis and absorption of the entire conceptus 

 have never heretofore been reported. Retention of the conceptus after 

 the death of the embryo is extremely common and is the usual thing 

 in unprovoked abortions. Of 2,000 cases in the Carnegie Collection, 

 12.8 per cent showed advanced intrauterine disintegration, only villi 



