120 ALAN C. SUTTON 



work upon the adult neuro-muscular spindles, that I began the 

 present line of research. I had in mind at the time more the 

 idea of merely completing the picture already two-thirds done 

 than of adding anything of real value, realizing, however, that as 

 in other investigations where embryological study has been the 

 first to throw light on the complex adult picture, so here too in the 

 simplicity of the early development I might be able to expose 

 important structures later obscured by the intricate form of the 

 fully-grown spindle. 



The first things that require consideration in work of this char- 

 acter are the selection of material and the methods best adapted 

 for solving your particular problems. I was fortunate in not 

 having any difficulty about getting material, as we receive at 

 the laboratory a daily supply of embryo pigs in utero from the 

 slaughter-house near by, so warm that frequently the hearts are 

 still beating. In this problem of the development of muscle- 

 spindles, an abundance of material is the most essential thing, for 

 the value of any conclusions varies directly with the number of 

 observations one is able to make. Then too, the early develop- 

 ment of the pig corresponds very closely to that of the human in 

 the many points where comparisons have been made. With any 

 method for staining nerve endings there are many possible pit- 

 falls. I found that it w^as not only necessary to work up one set 

 of specimens, from each stage of development, but to repeat these 

 observations time and again upon new material. My procedure 

 was to take whatever length pigs came each day, using the larger 

 sizes only at first, however; work them up and file away my 

 sketches and observations under that particular size without 

 regard to any previous findings in the pigs of that length. In 

 this way I accumulated in time a rather complete series ranging 

 at about 5 to 10 mm. intervals from 1 to 20 cm. In addition, 

 I had numerous observations on each length, made at various 

 times upon pigs from different litters. As a result, I feel that 

 I have been able to eliminate to a great extent personal errors in 

 observation and judgment. 



When I began this work I used gold chloride preparations of 

 the muscle to bring out the nerve endings, following out the 



