28 STUDIES ON PATHOLOGIC OVA. 



arranged from the card catalogue, a plan we have found essential in order that 

 any given type of specimen may be located easily. By this time the specimen is 

 fully recognized as normal or pathological, and it has also been determined whether 

 new records or drawings should be made for future reference. The photographs, 

 negatives, letters, notes, and drawings are then filed in numerical order in suitable 

 metal cabinets in a fire-proof vault. 



An effort is made to cut into serial sections, as soon as possible, all small embryos 

 that are well preserved. Miscellaneous specimens are likewise constantly being 

 sectioned for instance, an ovary, villi, portions of a chorion, or parts of larger 

 embryos. In order that this may be done without confusion to the investigator, 

 we have found it helpful to record each block under consideration upon a form 

 somewhat similar in character to figures 1 and 2; this we call the histological 

 record, which may be compared to a bill of lading. This sheet is dated and the 

 part of the specimen to be cut is indicated thereon, as are also the directions for 

 embedding, cutting, staining, etc. After the work has been done, the technician 

 returns the slides, with the histological record, to the investigator interested in 

 this particular specimen, who checks up the sections and enters the grade upon 

 the histological record, which is then placed in the permanent file. 



Preparations of many specimens for the microtome are constantly under way. 

 Since most of the specimens are delicate and can not be touched, we have had very 

 satisfactory results from passing them through the graded alcohols in shell vials, 

 closely stoppered with absorbent cotton. Within each vial is a loose tag bearing 

 the number of the specimen. Experience has taught us that if there is very careful 

 gradation only five grades of alcohol are necessary, beginning with 60 per cent, then 

 70 per cent, and so on. With the firm cotton stopper the entrance of the alcohol 

 is so gradual as to equal an infinite number of gradations. For instance, if the speci- 

 men is changed from a 60 per cent to a 70 per cent solution, the stopper should be so 

 tight that the diffusion can not become complete for several hours. When passing 

 from lower to higher grades it is preferable to invert the vial. If this were not done, 

 the stronger solution would not enter so quickly, as a 60 per cent fluid has a higher 

 specific gravity than a 70 per cent, and hence there would be a slower mixture. In 

 passing from stronger alcohol to water, on the other hand, the vial should be right 

 end up. The underlying idea of this procedure is based upon the fact that if the 

 ovum is thrown into strong alcohol, the chorion and outer layers of the embryo 

 become greatly shrunken, while the deeper tissues are well preserved, as the alcohol 

 diffuses slowly towards the center of the embryo. After dehydration the specimen 

 is embedded in either celloidin or paraffin, stained, and cut according to the direc- 

 tions given on the histological record, and is then ready for permanent filing. 



We have found it convenient to segregate the specimens into two groups. 

 The first includes all embryos which have been cut into serial sections. These 

 are filed according to length, so that any one wishing to study structures in the 

 4-mm. stage, for instance, will find all such embryos together in the cabinet. 

 There is, however, a very large amount of miscellaneous material which we have 

 been compelled to file merely in numerical sequence, and this constitutes the 



