148 Williolm TT 



enlarged to the same scale. Photogra])hy, as well as a new instrument 

 which he invented, the embryograph, aided him in his work. In order to 

 be better able to compare stage with stage, the reconstructions were con- 

 verted into models which were duplicated by Ziegler; these models now 

 form the most valual)le asset of many of the embryological museums the 

 world over. More accurate models can be made by drawing the sections 

 upon wax plates which when placed upon one another reproduce the 

 embryo ; this method, invented by Born, was used to a very great extent 

 by His in his later years. 



Until this time the embryological campaig-n had been conducted by 

 His from all sides, but one great fortress, the human embryo, still stood 

 before him. Human embryos were very difficult to obtain and the litera- 

 ture npon the subject was meagre and poor, but His -was soon able to 

 select a few important stages from a mass of poor material, normal and 

 pathological. These he studied with such care that the knowledge of the 

 anatomy of the human embryo now exceeds that of any other animal. 

 To be sure the earliest stages were missing, but this mattered but little, 

 for being master of the whole field of anatom}^, he was able to produce a 

 model work. Each chapter in his monograph is great and original, 

 giving a mass of information; the work reaches its climax of interest 

 and value in the part on the nervous system. 



During the last dozen, years of his life, His's attention was taken away 

 from the study of the nervous system by a variety of subjects; thus, for 

 example, he was interested constantly, as his letters show, in the 

 embryology of fishes." The work on this latter snbject he was able to 

 round out, but it seemed as if his promised work upon the brain would 

 never appear. When I visited him the summer before his death, I found 

 a broken man, working away at a large manuscript which by no means 

 satisfied him. What could be arranged, was published in a monograph 

 upon the brain, which will serve as a foundation for investigation for 

 many years to come. He had hoped to write another volume, but his 

 illness rapidly grew worse, and, unal)le to work longer, a week before 

 his death, he wrote that his remaining wish was that the end might 

 come soon. 



The technical ability of His which had been pretty well trained in the 

 gymnasium, gradually developed farther and proved to be of great value 

 to him as a teacher. Optical instruments of all kinds, magic lanterns 

 and microphotographic apparatus were much used by him ; demonstra- 

 tions with the microscope after each lecture aided in illustration. The 

 pictures wdiich he drew npon the board vrhile lecturing were models of 

 their kind and he developed them before the students in such a manner 



