50 FRANKLIN P. MALL 



onihryos. T haAo pi-fniously discussed tho rjuostion of cyclopia 

 in a sr])ai'at(^ puhlicatiou, and it is not therefore necessary for 

 me to dilate further ui)on it at ])resent."- Hare lip is also sharply 

 defined in the embryo and is as readily recognized as exomphaly. 

 Other anomalies, however, are more difficult to recognize as 

 sharply defined malformations in the embryo. 



We have in our collection about 2000 embryos. The patho- 

 logical specimens of the first 400 were reported in my paper on 

 the origin of human monsters mentioned above. Since the 

 collection was taken over by the Carnegie Institution of Wash- 

 ington, it has gTown at a very rapid rate, about 400 specimens 

 being added to it each year. I have in preparation a more ex- 

 tensive study of pathological embryos, and during the past year 

 have practically completed a careful study of the first thousand. 

 While this was in progress, another thousand specimens were 

 added to the collection. At present, however, only the first 

 thousand will be considered, the remainder not having been 

 sufficiently tabulated to be of statistical value. 



We have introduced and are gradually perfecting a system 

 of classification of the embryos which will enable us to locate 

 any specimen in our collection and the record thereof by means 

 of a card catalogue. Reasons for adopting this S3''stem were 

 given in a circular recently published.-^ The specimens can 

 clearly be divided into two groups according to their origin, 

 i.e., uterine and ectopic. In both of these, the embryos which 

 are normal in form are catalogued according to their sitting 

 height, which we call crown-rump (CR). All embryos there- 

 fore which are apparently normal, say 10 mm. long, are entered 

 upon one card. What happens to these specimens subsequently, 

 whether they are dissected, sectioned or preserved permanently 

 as whole specimens, may also be entered upon this card without 

 interference with the system of classification. The chief dif- 

 ficulty is to determine what constitutes a normal embryo, and 



- Mall, F. P. Cyclopia in the human embryo. Contributions to Embry- 

 ology, vol. 6, Publication No. 226, Carnegie Institution of Washington, 1917. 



^ Mall, F. P. Embryological collection of the Carnegie Institution, Circular 

 No. 18, 1916. 



