SECT. 3. J INTRODUCTION. 5 



were the only possible or existing elements of animals. Schwann's 

 ideas also of the origin of cells, although considerably modified 

 and extended, have not been essentially altered, the cell-nucleus 

 being always present as the principal agent of cell-formation 

 and multiplication. We have advanced least with reference to the 

 laws which prevail during the origin of the cells and higher ele- 

 ments, and our knowledge of the elementary processes during the 

 formation of the organ must likewise be designated as being still 

 very defective. Yet the proper path for clearing up these points has 

 been taken ; and a consistent investigation of the chemical con- 

 ditions of the elementary parts and of their molecular forces, as 

 it has been conducted by Donders, Dubois, Ludwig, and others, 

 together with a more and more searching microscopical analysis of 

 them which has been so useful in the nervous system and muscular 

 fibres, and a histological treatment of embryology Avhich has been at- 

 tempted by Reicliert, Vogt, myself and Remak, will certainly lift 

 the veil more and more, and lead step by step nearer to the per- 

 fection of the science, although that may never be quite attainable. 



§ 3. The aids in the study of Histology can only be shortly 

 mentioned here. With regard to literature, the more important 

 monographs will be found cited in the individual sections, and 

 only the larger independent works will be enumerated here. 

 Schwann's Jficroscopical Investigations on the Accordance in the 

 Structure and Growth of Plants and Animals, Berlin, 1839 (pub- 

 lished in English by the Sydenham Society in 1847), deserves the 

 first place, as the most fitting introduction to Histology. Besides, 

 we have to mention X. Bichat, Anatomic Generale (torn. iv. Paris, 

 1801) ; E. H.Weber, Handbook of Human Anatomy by Hildebrandt 

 (vol. i. General Anatomy, Brunswick, 1830) — an excellent work 

 for that period, and even yet indispensably necessary, both as such 

 and as a mine for the older literature; Burxs' Text-book of General 

 Unman Anatomy (Brunswick, 1841) — very clear, concise, and 

 good; Henle, General Anatomy (Leipsic, 1841), Avith a classical 

 exposition of our knowledge of the elementary parts in 1840, nu- 

 merous original statements, and physiological, pathological, and 

 historical remarks; G.Valentin, article "Tissue," in Wagner's 

 HandwSrterbuch der Physiologie(\o\.i. 1842); Quain and Sharpey's 

 Anatomy (3 vols. London, 1845 — 47, 6th edit. Loud. 1856) — the 

 histological part done by Sharpey most excellently ; R. B. Todd 

 and W. Bowman, The Physiological Anatomy and Physiology of 

 Man (2 vols. London, 1845 — 57) — based principally upon inves- 



