REVIEWS. 



TJie Cell Doctrine ; its History and Present State, hy James 

 Tyson, M.D. Philadelphia: Lindsay and Blakistou. 



Whilst America is perhaps not doing her share of the 

 work of original observation in the various branches of natural 

 science, we have from time to time abundant proof that her 

 scientific teachers are keeping abreast of the knowledge of 

 the day. Dr. Tyson, who lectures on the microscope and 

 physiology in Philadelphia, has produced in this book an 

 admirable resume of the history of the various theories and 

 observations on the ultimate structure of organic beings. 

 Wliilst giving credit to the earlier observers with the mi- 

 croscope, for their views and observations, he rightly speaks 

 of the researches of Schleiden and Schwann as having intro- 

 duced a new era into the history of our knowledge of animal 

 and vegetable structure. He passes successively in review the 

 observations of Henle, von Mohl, von Baer, Beale, Bennett, 

 and the views of Huxley. Without going into elaborate detail, 

 he presents the subject in such a way that the student can- 

 not fail to understand the exact bearing of the views of each 

 particular writer, on the subject of what is called " cell- 

 doctrine," or the " cell-theory." The author sums up his 

 own views in the following passage. 



" In conclusion, then, it may be stated, 1st, that the ' cell,' 

 or ' elementary part,' originating only in a pre-existing cell, 

 is the ultimate morphological element of the tissue of animals 

 and jilants. 



" 2nd. That the cell, contrary to the belief of the earlier 

 histologists, and, indeed, many later observers, is rarely 

 vesicular in its structure, but generally more or less solid 

 throughout. 



" ord. That the cell is composed of 'germinal' or living 

 matter which is central, and includes ' nucleus,' ' endoplast,' 

 ' protoplasm,' and ' sarcode ;' and of ' non-germinal,' or 

 ' formed ' matter, which is peripheral, and corresponds with 

 'cell- wall' and 'intercellular substance.' 



" 4th. That this germinal matter of the cell in a part or all 

 of its substance, may assume a special morphological state, 

 usually round or oval, commonly known as the 'nucleus' of 

 the cell, which, when present, is always a young centre of 

 germinal matter; but that in other instances both animal and 

 vegetable cells may be complete without this special form of 



