4 APPENDIX. 



engaged in this species of investigation, J. F. Meckcl is entitled to much confidence on 

 account of his talents and industry, and the results of his labours claim particular no- 

 tice, as they confirm much that has "been recorded by former observers. 



According to the views of this physiologist, the solids and fluids of the human body 

 may be reduced to two elementary substances : the one is formed of globules, the other 

 of a coagulable matter, which, either alone or united to the former, constitutes the liv- 

 ing fluids, when it is in the liquid state, and gives rise to the solid tissues when it as- 

 sumes the concrete form. 



The globules present, in their nature and aspect, differences which are relative to 

 the situations in which they are examined. They appear in the blood, flattened, and 

 composed of a central part which is solid, and of an exterior portion, which is hollow 

 and vesicular. Those found in the kidneys are smaller than those of the spleen ; and 

 the globules of the liver are still smaller. Those contained in the substance of the 

 nerves present a less volumn than those observed in the blood. 



Globules exist not, according to Meckel, in the proper structure of cellular tissue, of 

 fibrous and cartilaginous parts, and of the bones. On the contrary, they abound in 

 nerves and muscles, and determine their nature and colour. Some of the fluids, also, 

 as the urine, contain no globules, whilst they are abundant in the blood, in the ch}le, 

 the lymph, milk, &c. 



During the hrst period of conception, the mucous and homogeneous mass which con- 

 stitutes the embryo, contains no globules ; it is not until a more advanced period that 

 it is composed of two substances, the one fluid, the other solid. These two elements 

 seem to influence the form of the fibres and plates in which animal substances are dis- 

 posed. The laminated tissues arise almost exclusively from the fluid matter. The 

 fibrous tissues may also be produced from this matter alone, as in the tendons, &c. ; 

 they are, however, more frequently formed from the union of the globules with the 

 concretive fluid, as may be observed in the nervous and muscular textures. 



These observations of Meckel respecting animal organization, it ought to be noticed, 

 bear a near resemblance to the opinion entertained by Pfaff, who considered the ele- 

 mentary tissues to be formed from a series of molecules and globules, and to be diffe- 

 rent according to the presence and influence of the latter form of matter. The idea 

 of a fluid substance, capable of concretion, is analogous to the opinion of the ancients 

 especting the substance denominated by them gluten. It is the cellular tissue, accord, 

 ing to Meckel, which represents that substance ; and, in fact, he regards this tissue as 

 a species of concrete fluid, possessed of the properties already indicated. 



It must, in our opinion, be admitted that the theory of Meckel possesses claims to a 

 favourable notice. It is the result of observations which accord with those of others ; 

 it is also simple, and is easily to be reconciled with the phenomena which living tex- 

 tures present. 



Dr. Meyer, of Bonn, (Journ. Complem. dee Scien. J\Tcd. Nov. 1821.) also considers 

 that two kinds only of elementary texture exist in animal bodies. The one is, accord- 

 ing to him, composed chiefly of capillary vessels, and is formed from the assemblage of 

 these vessels : under it he arranges cellular, serous, fibrous, and mucous tissues : tho 

 other possesses a proper and peculiar parenchyma, composed of globules, or of an or- 

 ganic pulp ; such are the glands, the bones, muscles, nerves, the brain, and spinal 

 cord. The first set of organs is a continuation, in his opinion, of the vascular system ; 

 while the second, on the contrary, is farther removed from such a connexion. Foreign 

 substances introduced into the circulation, pass immediately, and with rapidity, into the 

 former textures, while they either fail altogether in penetrating, or insinuate themselves 

 much more slowly, and after quite a different manner, into the parenchyma of the lat- 

 ter organs. The one class seems to appertain in general to the system of secretion ; the 

 other class of textures neither secrete from their individual influence, nor can they of 

 themselves add to their nutrition. The first appears to be nourished by the imme- 

 diate, rapid, and continual access into the fluid part of the blood ; the second by a slow 

 and periodic deposition, and conversion into their proper substance, of the sanguine- 

 ous globules of the blood, by means of the influence of the vascular extremities upon 

 the blood which they contain. 



The primary solids, or rather, the elementary fibres* of the human body, and of the 



* It should be kept in recollection that fibre is used as signifying an elementary ani- 

 mal substance ; tissue indicates a certain arrangement of the former a peculiar struc- 

 ture of parts : and organ signifies a compound or complex part which performs func- 

 tions peculiar to itself. 



