238 The Microscope. 



In the April number of the same journal can be found a paper 

 by Dr. Abbott, who is a most devoted pupil of Heitzman, on the 

 structure of the enamel. Heitzman beautifully pictures this delicate 

 net-work as ever present between the so-called enamel rods. In 

 fact he, with Abbott, claims that even in the hardest substance in the 

 body, the enamel, there is to be seen this ever-present reticulum. 



Now it seems that Dr. Allan conceived the idea that an exami- 

 nation of the very specimens used by these investigators to make 

 new theories fi'om, might be convincing to him ; for the most patient 

 work on his part had never shown him this beautiful net- work. 



" An examination of the specimens " used by Heitzman and 

 others, and from which these lieautiful drawings are made, is what 

 many of us have long desired to do. Dr. Allan obtained some of 

 these slides and some were also sent to Dr. Andrews, of Cambridge, 

 Mass., " whose position as an acknowledged authority in such mat- 

 ters is unquestioned." 



Dr. Allan examined these slides with a Powell and Leland im- 

 mersion, ^ ; a Hartnack im., yV ; a Gundlach im.. j-^, " all superior 

 glasses, and every care was taken in all their adjustments and in 

 managing the illumination." Each observer worked entirely inde- 

 pendent of the other. What was the result ? Dr. Allan says : " The 

 ivriter could not make out any reticulum, nor in fact anything re- 

 sembling one. The specimens tvere tvorthless for the purpose in- 

 tended.'^'' He, therefore, denied the existence of the protoplasmic 

 reticulum as described by Abbott, Bodecker and Heitzman, said 

 denial being based upon an examination of their own preparations. 



But Dr. Andrews writes: ''I have examined many slides of 

 thin enamel, some of which were examined by Heitzman in his labor- 

 atory, and pronounced by him to show the reticulum. These speci- 

 mens I have examined critically, with a most excellent ^ of Tolles. 

 and am assured that nothing like a reticulum figured by him can 

 be demonstrated in them. In regard to the study of Prof. Abbott's 

 slides, loaned for that purpose, I could find no appearance whatever 

 of fibrils resembling the exquisite drawings made by Heitzman, il- 

 lustrating the article in the April Cosmos." And yet from these very 

 slides ai'e made the "exquisite drawings" of the author of this new 

 departure ! 



Ann Arbor, Mich. 



