4 MANUAL OF HUMAN MICROSCOPIC ANATOMY, [sect. 2. 



If it be asked how Histology responds to these desiderata, and 

 what prospects it has for the immediate future, the answer is by 

 no means satisfactory. Not only does it not possess a single 

 law, but even the material from which laws are to be deduced is 

 still relatively so scanty, that not even a large number of general 

 propositions appear to be secured. Not to speak of a complete know- 

 ledge of the intimate composition of animals in general, we do not 

 know thoroughly the structure of any creature, man not excepted, 

 although he has so often been the subject of investigation, and, 

 accordingly, it has not yet been possible to bring science essentially 

 nearer to its aim. It would, however, be improper to overlook 

 and depreciate what we possess ; and it may be affirmed, that a 

 rich treasury of facts, and even some valuable general propositions 

 have already been won. To indicate only the most important of 

 the former, it may be mentioned, that we possess a very satisfactory 

 knowledge of the fully developed elementary parts of the higher 

 animals, and with the exception perhaps of the elastic tissue, the 

 tissue of the bones, and of the elements of the teeth, are sufficiently 

 informed of the progress of their development also. The mode in 

 which they unite to form organs has been less investigated; yet even 

 in this particular much has been done of late, especially in man, 

 whose individual organs, with the exception of the nervous system, 

 the higher organs of the senses and some glands (liver, and vascular 

 glands) have nearly been thoroughly investigated. If the doings in 

 this department follow each other in the same. Way as heretofore, the 

 human structure will, in a few years, be so well known, that with 

 the aids at our command at present, nothing essential, except, per- 

 haps, in the nervous system, will remain to be done. It is different 

 with Comparative Histology, which has scarcely been commenced, 

 and which, from the mass of material, will require not years but 

 tens of years for its mastery. Whoever ivould perform something 

 useful in this department, must provide himself with a survey of all 

 divisions of animals by monographs of typical forms, embracing their 

 total structure from the first development onivards, and then en- 

 deavour to develop the laius in the manner above mentioned. 



With regard to the general propositions of Histology, the science 

 has not advanced materially since Schwann's time. Nevertheless, 

 much has been gained, inasmuch as Schwann's doctrines are now 

 established in their main features. The assertion, that all the 

 higher animals at one period consist solely of cells, and that their 

 higher elementary parts are developed from these, stands fast, 

 although it is not to be understood as if cells or their derivatives 



