Yi; 
ANIMAL TISSUES. 14 
different layers: the finest vessels (called Capillaries) of a 
single uniform membrane, without fibres or other tissue, 
but in which lie round or oblong microscopic corpuscles 
(cell-nuclei). In the larger blood-vessels, and also in the 
lymphatics, the innermost coat is formed of cells, which, 
as in the Cuticle, lie side by side, pavement-fashion. This 
coat is covered by others which present fibres partly longi- 
tudinal, partly circular. Then comes the most external 
layer of conjunctive tissue, which connects the vessels with 
the neighbouring parts. 
Nervous Tissue (tela nervea). To this belongs in the higher 
animals, the brain, the spinal cord, the ganglia and the 
nerves: inferior animals have only nerves and ganglia, 
which last take the place of the central parts of the nervous 
system. The chemical constituents of this tissue are 
Albumen and a species of Fat containing Phosphorus. 
The nerve-stems and the bundles of which they consist, 
are surrounded with coats of conjunctive tissue, called 
Neurilema: dilute muriatic acid dissolves the neurilema: 
alkaline solutions, on the contrary, cause the nervous 
medulla to disappear, the neurilema remaining alone. The 
nerves consist of fine threads, which neither subdivide, nor 
anastomose with each other. They are of very unequal 
thickness, ;...to ; millim. and less, especially in the 
nerves of sense. Besides these threads there are found 
corpuscles with nuclei: these present themselves in the 
ganglia and in the grey substance of the brain and spinal 
cord. These ganglion-corpuscles are very dissimilar in 
form and size, mostly ;...4 millim. 
Horny Tissue (tela cornea). The parts consisting of this 
tissue have neither blood-vessels nor nerves. Cuticle, nails, 
hair, feathers, horns and scales belong hereto. They lie on 
the surface of the body, whilst a covering (epithelium), resem- 
bling Cuticle, lines the inner surface of the mucous membranes 
(as of the stomach) and also of the internal closed cavities 
and sacs, as well as of the vessels (see above, III. Vase. 
Tis.). ‘The Cuticle, or Epidermis, consists of microscopic flat 
cells joining on to each other like a pavement, and of which 
each contains a nucleus. Water swells up the epidermis, 
