First lines of physiology, being an introduction to the science of life; written in popular language . termed by phy-siologists the cellular tissue. It is important that youshould remember that both the terms just defined areoften employed, indiscriminately, with the same meaning. 68. The cellular membrane that appears to form thewhole body of the hydra, is found in all animals in greatabundance, but is diflferently arranged according to theparticular class of animals in which it is observed. In I JTATURE OF CELLUr^AR TISSUE. 51 man, if we examine a single film of this tissue, under astrong mi
First lines of physiology, being an introduction to the science of life; written in popular language . termed by phy-siologists the cellular tissue. It is important that youshould remember that both the terms just defined areoften employed, indiscriminately, with the same meaning. 68. The cellular membrane that appears to form thewhole body of the hydra, is found in all animals in greatabundance, but is diflferently arranged according to theparticular class of animals in which it is observed. In I JTATURE OF CELLUr^AR TISSUE. 51 man, if we examine a single film of this tissue, under astrong microscope, we find that even the sides of the cellsare evidently composed of very minute fibres, with in-tervals between them too small to allow the most search-ing liquid to flow readily through the tissue, but largeenough to make it less wonderful that this membraneshould be found capable of absorbing nourishment, andthat it should slowly transmit fluids in the form of vapour,as, in the sequel, you will find that it does. The fibrousappearance just described, is well displayed in fig. 5, Fig. Cellular membrane magnified. which represents a film of cellular tissue, highly magni-fied. On increasing the power of the microscope stillfurther, the fibres seem to be composed of rows of glo-bules : but all observations made with instruments ofsuch prodigious power, are very apt to produce decep-tive appearances. Those of you who have ever seenan animal skinned, may have noticed that the skin isattached to the body by a white or transparent sub-stance, which may be torn very easily in many places,but, in other situations, it requires to be cut before theskin can be detached. This is the cellular membraneor cellular tissue. 69. To show that the cells communicate with eachother, it is only necessary to mention that dishonest peo- 52 NATURE OP CELLULAR TISSUE. pie, when preparing chickens or other small animals formarket, not unfrequently introduce a small pipe throughthe skin, and bl
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