Joseph Marshall Flmt 271 



perfectly the form and relations of the original tissue. It is the delicate 

 opaque skeleton of the original tissue formed by the connective tissue 

 frame-work, and when viewed through the stereoscopic microscope, 

 shows in three dimensions all of the normal relations of the frame-work 

 to the original structures of the organ. Owing to the high diffraction 

 of the fibrils many of the finest details of structure are brought out, as 

 for example, the basement membranes of the alveoli, ducts, vessels, 

 perilobular membranes, etc. When pieces of the submaxillary gland are 

 digested and cleared in this way, the ducts and their accompanying 

 vessels are shown beautifully, both in the interlobular spaces and as 

 Ihey enter the lobule and ramify in its substance. 



After careful drawings have been made of these thick preparations 

 in glycerine, they can be utilized for further study with the finer meth- 

 ods according to the original procedure of Spalteholz. When embedded 

 in paraffin and cut in thin sections, they can be stained on the slide 

 with iron hgematoxylin. Numerous variations in the stains are, of 

 course, possible although iron hgematoxylin and aniline blue give by far 

 the sharpest pictures. Beautiful specimens can be obtained by using 

 celloidin as an embedding mediimi and cutting thick sections which are 

 stained in an eight per cent solution of acid fuchsin. They are then 

 washed rapidly in distilled water and the graded alcohols until the 

 celloidin is decolorized, and finally cleared in creosote and mounted. 

 These preparations show the fibrils distinctly for naturally the staining 

 adds greatly to the clearness of the picture, but, at the same time, it is 

 necessary to sacrifice some of the depth as the stained sections cannot 

 be cut over a certain thickness, depending partially on the nature of 

 the tissue and partly on the density of the meshwork. 



For the study of the ducts in sections most of the ordinary proced- 

 ures were employed. Several proved especially useful for this purpose, 

 among which was the method of slide digestion perfected by Spalteholz 

 and his pupils.* This consists, briefly, in mounting an alternate series 

 of paraffin sections and digesting one with pancreatin, while the other 

 is stained as a control. To complete this comparison the writer treated 

 a third section by Weigert's elastic tissue method counterstained with 

 picric acid, so as to have, side by side, successive sections prepared by 

 three different methods instead of two. Hensen's modification of the 

 Van Gieson stain ° proved of value in the study of the connective tissue 



^Spalteholz: loc. cit. Hoehl : Arch. f. Anat. u. Phys., Anat. Abtlg., 1897. Clark: 

 Ibid., 189S. 



"Hensen: Anat. Anzeio'er., Bd. xr. 



