Mabch 15, 1918] 



SCIENCE 



257 



upon solving problems; it lay in under- 

 standing principles rather than in multi- 

 plying evidence. 



We have outlined Dr. Mall's work in 

 anatomj- as it grew out of his studj' in Lud- 

 wig's laboratory. But he was not only an 

 anatomist, he was also an embryologist. 

 In 1891 he published an account of a nor- 

 mal human embryo, now placed in the 

 fourth week of development. He made a 

 most careful and accurate study of all of 

 its systems, illustrated by the surface form, 

 by models and casts. This was the first hu- 

 man embryo ever modeled in America and 

 at that time it was the most complete ac- 

 count of anj' human embryo in existence. 

 In this stud}' he announced several discov- 

 eries, for example, that the Eustachian tube 

 and the middle ear arise from the first 

 branchial arch. The effect of this work on 

 Dr. Mall is to be seen in these words in one 

 of his publications : 



I always think in human anatomy in relation to 

 this embryo. 



Dr. Huber has said that this study has 

 served as a model for all future work of 

 its type. It did more for, like his work 

 on the stomach, it represents as it were. Dr. 

 Mall 's program in embrj'ology. This speci- 

 men forms the foundation of the priceless 

 collection of over two thousand human 

 embryos which Dr. Mall later gave the de- 

 partment of embryology of the Carnegie 

 Institution of Washington. It was perfect, 

 beautifully fixed and sectioned. When he 

 had finished the description of it he offered 

 it as a tribute to his teacher. His. His re- 

 turned it, with several others of his own, 

 expressing the wish that they might be the 

 nucleus for a much larger collection. How 

 richh- has this gift borne fruit in the de- 

 velopment of the science of embryologj'! 



In the study of embryonic development, 

 three names stand out in logical sequence, 

 von Baer, His, Mall. Neither His nor Dr. 



Mall were concerned with the phenomena 

 of maturation, fertilization or the cleavage 

 stages, in the development of the embryo, 

 but the latter has characterized the work of 

 His as laying a foundation for histogenesis. 

 In like manner the work of Dr. Mall in 

 normal embryology may be summed up in 

 the term organogenesis. He has traced the 

 growth of organs up to their adult stage. 

 He has laid the foundation for a complete 

 anatomical survey of the human embryo in 

 all stages of its development. Here, for ex- 

 ample, belong his studies on diaphragm 

 and the ventral abdominal walls and more 

 strikingly his studies on the development of 

 the loops of the intestine. These he fol- 

 lowed from their beginning up to their 

 position in the adult, he then determined 

 their normal position in the adult by stud- 

 ies in the dissecting room, and by experi- 

 ments on animals he showed that both the 

 intestine and the omentum seek their nor- 

 mal position when disturbed. Of this work 

 His wrote : 



Your satisfaction in your work will be lasting, 

 because you have brought light into a field which 

 was so obscure. The thing which has been lacking 

 in all of our studies on development up to this time 

 has been observations on the transition between 

 the early embryonic and fetal stages up to the form 

 of the adult. For the intestine you have given the 

 entire study from the beginning up to the end, 

 and I regard it a great step in advance. 



It is in connection with the development 

 of the vascular system that Dr. Mall made 

 some of his most significant contributions 

 to embryology. One of the most important 

 points in the study of the embrj'o just 

 mentioned was solving the problem of the 

 primitive ventral branches of the aorta. 

 This he did by showing that the vessels 

 which are the forerunners of the celiac axis 

 arise as far forward as the first dorsal seg- 

 ment and bj' indicating the method by 

 which they shift back to their position in 

 the adult. This work has since been repeated 



