PRKFACE. IX 



Histology, and to form a collection of preparations of the elementary 

 tissues of both animals and vegetables, healthy and morbid, adapted to 

 illustrate the uses and results of microscopical investigations. From 

 that time histological anatomy deservedly became an important branch 

 of the education of the medical student. 



By " conducting the eye to the confines of the visible form," the 

 ^licroscope proves an effective auxiliary in defining the geometric pro- 

 perties of bodies. Its influence as an instrument of research upon the 

 structure of bodies has been compared to that of the galvanic battery, 

 in the hands of Davy, upon Chemistry. It has enabled us to detect 

 the smallest structural difference, heretofore inappreciable ; and in our 

 analysis to define positively the structure of tissues beyond the capa- 

 bility of the greatest magnifying power to change or modify. 



The Microscope, as an ally of Chemistry, enables us to discover very 

 minutely and completely the changes of form and colour effected by 

 test-fluids upon solids ; it dissects for us, so to speak, the most multi- 

 plex compounds ; it opens out to the mind an extended and vast tract, 

 opulent in wonders, rich in beauties, and boundless in extent. 



In prosecuting the study of Vegetable Physiology, the Microscope 

 is an indispensable instrument ; it empowers the student to trace the 

 earKest forms of vegetable Ufe, and the functions of the different tissues 

 and vessels in plants. Valuable assistance is derived from its agency 

 in detecting the adulteration of our articles of food, as has been verified 

 by the exposures — ^which must have done great good — that have from 

 time to time appeared in the Lancet, and subsequently collected into a 

 volume by Dr. HassaU. In the examination of suspected flour, an 

 article of so much importance to all persons, the Microscope enables tis 

 to judge of the size and shape of the starch-grains, the markings of 

 &em, and their isolation and agglomeration, and thus to distinguish 

 the starch-grains of one meal from those of another. In the necessarily 

 limited space of this work, the author has only been able to glance at 

 the subject of the minute structure of vegetables ; but the remarks and 



