Purchase of this book includes free trial access to ... where you can read more than a million books for free. Excerpt from book: Section 3CHAPTER IV THE CELL AND THE TISSUES The term cell was originally applied to a small enclosed apartment or room set apart as the living quarters of a monk or hermit. Thus in the seventeenth century, when early microscopic examination of various tissues was made the term cell was applied to the compartment-like spaces observed in these tissues. These investigations were carried on by Hooke ...
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Purchase of this book includes free trial access to ... where you can read more than a million books for free. Excerpt from book: Section 3CHAPTER IV THE CELL AND THE TISSUES The term cell was originally applied to a small enclosed apartment or room set apart as the living quarters of a monk or hermit. Thus in the seventeenth century, when early microscopic examination of various tissues was made the term cell was applied to the compartment-like spaces observed in these tissues. These investigations were carried on by Hooke, Grew and Mal- pighi, the latter being a name familiar to all students of anatomy. The nucleus was first prominently mentioned by Robert Brown in 1831. In 1838 the first proof that plants were made up wholly of cells was brought forward by Schleiden. With this as a foundation, it was a short step to the conception that the animal body was also built up of cells of a similar nature. Definition.?The cell may be defined as a textit{nucleated mass of protoplasm endowed with the attributes of life. The simplest forms of animal life are unicellular organisms called protozoa. It is significant that even the higher animals develop from a single cell, the fertilized ovum. This single cell by repeated division gives rise to a mass of similar cells, which as development proceeds becomes differentiated into three layers. The outer layer is called the ectoderm, the middle layer the mesoderm and the inner layer the entoderm. The further differentiation of the cells comprising these three layers is one of morphology; and through it is accomplished the ability to perform varying functions. Throughout the entire field of histological study the fundamental principle governing differentiation of form is found in the demands made upon the organism for the performance of different functions. The study of the minute structures of the teeth and their investing tissues emphasizes most strongly the relationship existingbetween form and fu...
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