32 Traxsactioxs of the Americax Ixstitute. 



Bcopic examination, and in tliis manner an immense amount of fraud 

 is prevented and an immense saving secured to the Government. A 

 very common form of adulteration in quinine and other valuable 

 powders used in medicine, is to mix with them powdered gypsum, 

 sugar or starch. The microscope infallibly picks out the fraudulent 

 particles, and the use of polarized light greatly facilitates tlie dis- 

 co verv. Each starch granule exhibits, indeed, with this species of 

 illumination, a distinct black cross, and, to use the words of the late 

 Horace Mann, in speaking of this fact, seems to be crying out with 

 all its might, "Potato Starch, his mark." 



The microscopic study of the elementary tissues of the higher order 

 of animals has also shown, along with a marvelous simplicity and con- 

 formitv of general plan, such endless variety of detail, and such constant 

 association of each variety with a particular natural group, that, in 

 the vertebrated series, it is almost invariably possible, by the examina- 

 tion of the minutest fragment of bone, for instance, to pronounce 

 with contidence as to the natural family to which it has belonged. 

 Tills is the more especially true in regard to the teeth, whose pecu- 

 liarities of structure have been so thoroughly studied and demon- 

 strated bv Prof. Owen, that it is, in general, possible to distinguish' 

 even genera and species. When it was announced that Baron Cuvier, 

 by the help of a single bone, as, for instance, a tooth, would under- 

 take to reconstruct the entire skeleton of the animal of which it had 

 been a part, the statement seemed almost to border on the incredible. 

 But to-day we may go further, and say that, as from the merest frag- 

 ment, we can reconstruct the tooth, so it is no longer necessary to 

 have a speciman of an animal large enough to be visible to the naked 

 eye in order to enable us to portray the animal himself. 



Wliat is true of the vertebrates is true to a great extent of tlie 

 other great sub-kingdoms of the animal world, the structure of their 

 liarder y^arts, the shells, for instance, of mollnsks, crustaceans, &c., 

 having a regularly organized structure, varying with the ditferent 

 groups, but invariable for the same, so that a microscopic fragment 

 of any such solid suffices, as a general rule, to fix the place of the 

 animal which produced it, in the scale of organic life. Similar dif- 

 ferences characterize the softer and more perishable parts of the 

 higher animals, the cartilages which cover the articulations, the liga- 

 ments which bind them together, the muscles which produce motion, 

 the tendons which transmit it, the brain, the ganglia, the nerve tubes, 

 the membranes and the skin. Of all, or most of these, the structure 



