PREFACE. 



Numerous as were the articles which, according to the first plan of the 

 work, were to have been introduced, it was soon found indispensable not only 

 to add others quite new, but also to enlarge considerably the space allotted 

 to each of those which formed the original catalogue, and to multiply greatly 

 the number of illustrations. 



All this was rendered necessary by the rapid strides which our know- 

 ledge of many subjects in Anatomy and Physiology began to take at the time 

 when the earlier parts of the Cyclopasdia made their appearance. Perhaps 

 there never was greater activity of research in any branch of science during 

 a given period, than that under which the sciences of Anatomy and Phy- 

 siology advanced during the last quarter of a century. Minute anatomy, 

 which thirty years ago was crude and undigested, now takes very high rank 

 among the various branches of Natural Knowledge. During these years every 

 tissue has been scrutinised ; many obscure points have been cleared up ; 

 much that was wholly unknown has been brought to light. The additions to 

 our knowledge of Anatomy, although there is yet ample room for fresh dis- 

 coveries, have given a totally new phase to Physiology. From being little 

 more than a series of vague and ill-founded hypotheses, scarcely deserving even 

 that name, it has become a well-arranged science, embracing a vast amount 

 of clearly defined facts, which, at once, form a solid basis for a superstructure 

 of sound theory, and throw much light upon the various processes of animal 

 and vegetable life. 



It was the constant aim of the Editor, where it was possible, to secure the 

 assistance of Contributors who would be likely to make original investiga- 

 tions, and to employ new researches for furnishing the materiel of their articles. 

 Whilst it is thankfully acknowledged, that in many instances the Editor's most 

 sanguine hopes were fully attained, it is not less true that he was sometimes 

 disappointed, and that much delay of publication and apparent breach of faith 

 took place. A few completely failed to fulfil their engagements, without any 

 assignable reason; others were unavoidably prevented from so doing. In 

 several instances the articles were not completed at the stipulated time. For 

 some of these the Editor was content to wait, notwithstanding that by so 

 doing the immediate sale of the book was injured, and the Editor himself 

 exposed (with apparent justice) to charges of violation of promises. But, in 

 the particular cases referred to, the Editor knew that delay in the comple- 



