CONNECTIVE AND VASIFACTIVE TISSUES OF LEECH. 315 
appears to me that the granules are similar to those of the 
brown-pigmented fibres, but of this I am by no means 
certain. 
Further, it appears exceedingly probable that these granules 
are of the same physiological nature as the yellow-brown gra- 
nules which load the endothelial cells of the coelom of the 
Earthworm and other Chaetopoda in the region of the alimen- 
tary canal. In the Earthworm these cells not only form a com- 
plete tunic to the intestine, but also invest the large blood- 
vessels. At the same time it must be distinctly pointed out 
that the cells which thus clothe the large vessels of the 
Earthworm and the contractile vascular caeca of Lumbri- 
culus are not the cells which form the proper wall of the 
blood-vessel, but lie externally to these. Hence their rela- 
tion to the vascular space and to the haemoglobin ous fluid is 
essentially difierent from that of the granular cells of the 
botryoidal vessels of the Leech. 
Previous ohservations relative to the brown fibres and 
botryoidal vessels of the Medicinal Leech, — It is not desirable 
to go over the history of a subject which has not of late years 
formed the subject of serious investigation. The opinion of 
Brandt that the botryoidal form of the vaso-fibrous tissue of the 
Leech was hepatic in character has never been maintained by 
any histologist. The two observers who have studied the Leech 
with the aid of the microscope, namely, Leuckart and Ley dig, 
have both rejected BrandFs view as to the botryoidal tissue, but 
have advanced divergent opinions of their own. 
Leuckart Die Menschlichen Parasiten,*’ vol. i) studied the 
anatomy of the Leech by means of transverse sections, and 
arrived at the conclusion that BrandPs hepatic tissue^^ was 
nothing more nor less than a mass of deep-lying epidermal 
glands. In this he was misled by the circular outline of the 
botryoidal vessels when in section, and by the fact, which he 
was the first to observe, that unicellular epidermal glands do 
travel very deeply into the body- wall of the Leech, and form 
groups of spherical cells, which are obvious enough in trans- 
verse sections (see Mr. Bourne’s fig. 13, Plate XXV). 
Leydig, in his ^Histology’ (1857), states: Relatively to 
the liver of the Leeches, properly so called, my observations 
compel me to differ completely from the prevailing opinion. 
Certain utriculi,of a brownish-yellow colour, which envelope the 
stomach and intestine, are commonly considered to constitute 
the liver ; these utricles open one into the other by means of 
their excretory canals, and pour their contents on to the internal 
surface of the intestine. Contrary to this view, I venture lo 
