VERTEBRATED ANIMALS. 253 



649, Although tnere would at first sight appear but little in common 

 between the simple bodies of those humble Monerozoa which constitute 

 the lowest types of the Animal series ( 392), and the complex fabric of 

 Man or other Vertebrates, yet it appears from recent researches, that in 

 the latter, as in the former, the process of ' formation' is essentially 

 carried-on by the instrumentality of protoplasmic substance, universally 

 diffused through it in such a manner as to bear a close resemblance to the 

 pseudopodial network of the Ehizopod (Fig. 283); whilst the tissues pro- 

 duced by its agency lie, as it were, on the outside of this, bearing 'the 

 same kind of relation to it as the Foraminiferal shell (Fig. 314) does to 

 the sarcodic substance which fills its cavities and extends itself over its 

 surface. For, as was first pointed out by Dr. Beale, 1 the smallest living 

 ' elementary part ' of every organized fabric is composed of organic mat- 

 ter in two states: the protoplasmic (which he termed germinal matter), 

 possessing the power of selecting pabulum from the blood, and of trans- 

 forming this either into the material of its own extension, or into some 

 product which it elaborates; whilst the other, which may be termed 

 formed material, may present every gradation of character from a mere 

 inorganic deposit to a highly organized structure, but is in every case 

 altogether incapable of self -increase. A very definite line of demarcation 

 can be generally drawn between these two substances, by the careful use 

 of the staining-process ( 200); but there are many instances in which 

 there is the same gradation between the one and the other, as we have 

 have formerly noticed between the ' endosarc ' and the ' ectosarc ' of the 

 Amoeba (403). Thus it is on the protoplasmic component that the 

 existence of every form of Animal organization essentially depends; since 

 it serves as the instrument by which the nutrient material furnished by 

 the blood is converted into the several forms of tissue. Like the sarco- 

 dic substance of the Rhizopods, it seems capable of indefinite extension; 

 and it may divide and subdivide into independent portions, each of which 

 may act as the instrument of formation of an 'elementary part.' Two 

 principal forms of such elementary parts present themselves in the fabric 

 of the higher Animals namely, cells and fibres ; and it will be desirable 

 to give a brief notice of these, before proceeding to describe those more 

 complex tissues which are the products of a higher elaboration. 



650. The cells of which many Animal tissues are essentially composed, 

 consist, when fully and completely formed, of the same parts as the typi- 



exceedingly fertile in results of this most intereating character. Thus Dr. N. 

 Kleinenberg, in his admirable " Anatomische entwickelungsgeschichtliche Un- 

 tersuchung" (1872), on Hydra, gives strong reason for regarding a particular set 

 of cells in the body of that animal as combining the functions of Nerve and 

 Muscle. And the Author has been led by his study of Comatula to recognize 

 the most elementary type of Nerve-trunk in a simple protoplasmic cord, not yet 

 separated into distinct fibres with insulating sheaths. 



1 Prof. Beale's views are most systematically expounded in his lectures On 

 the Structure of the simple Tissues of the Human Body," 1861; in his " How to 

 Work with the Microscope," 5th edition, 1880; and in the Introductory portion 

 of his new edition of " Todd and Bowman's Physiological Anatomy," 1867. The 

 principal results of the inquiries of German Histologists on this point are well 



stated in a Paper by Dr. Duffin on ' Protoplasm, and the part it plays in the 

 actions of Living Beings,' in " Quart. Journ. of Microsc. Science," Vol. iii., N.S., 



of any 



illogical to designate contractile muscular fibre (for example) as 'dead,' merely 

 because it has not the power of self -reparation. 



