16 INTRODUCTION. 
passage of the secreted fluid, which is conveyed into the intestinal 
canal or to the surface of the body. This efferent canal receives, 
like an arterial trunk, the finer canals which effect the secretion, 
and which are covered with epithelium. To such belong the 
kidneys, the liver, the salivary glands, &c. 
From what has been said, it is obvious that we cannot adopt 
that division of the Tissues which an esteemed writer! has pro- 
posed: into simple, constituent, and compound tissues. Doubtless 
every muscle contains nerves and blood-vessels, but nerves and 
blood-vessels are not on that account constituents of muscular 
tissue. According to our view, every tissue is simple, but it may, 
either by itself, form special parts, or only in combination with 
other parts. The corneous tissue is the only one which comes 
under the first head: all other tissues form this or that part, only 
in combination with one another: nervous tissue, for instance, does 
not by itself form a nerve, but only in combination with conjune- 
tive tissue and blood-vessels. Some of these compound tissues are 
distributed generally throughout the whole body, others are limited 
to certain parts. To the generally distributed belong conjunctive 
tissue, vascular tissue, and nervous tissue: the other tissues are 
appropriated to determinate parts of the body and have a greater 
self-subsistence, as cartilage tissue, muscular tissue, elastic tissue. 
This was the division formerly adopted by Bicnar. Other di- 
visions of the tissues, founded on chemical research, as into gelati- 
nous and albuminous tissues, may have their use in Physiology, but 
are not to be considered as anatomical divisions. 
The above tissues, then, build up the proximate organic con- 
stituents of the animal body. Formerly, when less weight was 
allowed to microscopic enquiry in general anatomy, the ultimate 
organic constituents in these tissues were neglected: but now their 
description forms a part of the description of the tissues themselves. 
In this way we have learnt to recognise in conjunctive tissue, in 
nerves, in muscles, &c. fibres as the ultimate elements of microscopic 
analysis: in cartilage, round or oblong corpuscles: in corneous and 
adipose tissues, cells. It may be asked, whether these organic elements 
can be deduced from one another ; or, in other words, whether all the 
1 E. H. WEpER in the 4th edition of F. H1npEBRANDT’s Handbuch der Anatomie 
des Menschen revised by him. Braunschweig, 1830. 8. s. 169—178. 
