458 
DE. HEEBEET WATNEY ON THE MINUTE 
Lipsky (43), 1867, noticed small round cells in the epithelium covering Peyer’s 
patches. 
Verson (45), 1870, also mentions the occurrence of rounded cells between the attached 
extremities of the epithelial cells over Peyer’s patches. 
Methods employed. 
Hardening in Chromic Acid. 
The intestine or stomach of a recently killed animal was washed as soon as possible 
in one tenth per cent, chromic acid, or in one per cent, bichromate of potash, and then 
immediately transferred to chromic acid. After the chromic acid, it was placed in forty- 
six per cent, spirit and finally preserved in spirit of the strength of ninety-two per cent, 
(ordinary methylated spirit). To obtain a very firm tissue it was left from seven to ten 
days in one fifth per cent, chromic acid, and then from two to five days in the weaker 
spirit, before being transferred to the stronger. 
To obtain sections which would show the lymph-corpuscles clearly differentiated from 
the other tissues, the stomach and intestine were hardened only four days in one sixth 
per cent, chromic acid, and then four days in the weak spirit, finally being placed in the 
strong. 
Hardening in Chloride of Gold and Chromic Acid. 
After washing the tissue in one tenth per cent, chromic acid, it was placed in one half 
per cent, gold chloride for four hours, and then in one sixth per cent, chromic acid from 
four to eight days, afterwards in the weak spirit one to two days, and finally removed 
to the strong. 
To obtain the Intestine of an Animal during the Absorption of Fat. 
Milk, or milk and cream, were given the animals to drink; or the cream was injected 
into the intestine (the latter was the plan pursued with hedgehogs), the animal in either 
case being killed one or two hours afterwards. 
Osmic-acid Staining. 
The following modification of Basch’s (46) method was employed : — The ligature 
intestine was placed in warm Muller’s fluid for twenty-four hours, and at the end of 
that time small portions were washed in one tenth per cent, osmic acid, and then placed 
in one to one half per cent, osmic acid for twenty-four hours ; they were further har- 
dened in one sixth per cent, chromic acid for six or eight days, left in weak spirit for 
two days, and afterwards transferred to the strong spirit. The latter was saturated with 
fat (oil and wax), so that the spirit might not dissolve the fat of the preparations. 
Staining of Specimens. 
The specimens (with the exception of some which were treated by osmic acid) were 
