94 A HALF-HOUR WITH THE 



which is called a nucleus, and this again another 

 little spot, which is called a nucleolus. The red 

 globules vary much in size and form in different 

 animals. Thus, in birds, reptiles, and fishes, they 

 are oval instead of round ; and, mostly, in these 

 three classes much larger than in mammals. This 

 is especially the case in the batrachian reptiles, to 

 which the frog and toad belong. Those from the 

 frog are shown at figure 8, plate 1. In the fowl, 

 shown at figure 7, and in the sole, seen at figure 9, 

 they are nearly twice as large as in man. In the 

 insects they are also frequently of large size, as in 

 the cockchafer, seen at figure 10. 



The proof that blood-stains have been produced 

 by human blood on articles of dress and other 

 things, is frequently important in medico-legal in- 

 vestigations. Although it cannot be distinguished 

 from all other kinds of blood, it may be from some ; 

 and the Microscope has been employed as an adjunct 

 in such cases. 



The structure of the skin, and other organs of 

 the body, are very interesting subjects for micro- 

 scopical investigation ; and volumes have been 

 written upon their diversified details. The struc- 

 ture of voluntary and involuntary muscular tissue 

 may be easily examined, especially the former, by 

 taking a portion of the flesh of any animal usually 

 eaten as food. The striated fibrillae of voluntary 

 muscle may be best seen in flesh cooked as food. 

 A muscle consists of bundles of fibrea and each of 

 these fibres consists of several fibrillse lying close 

 together. Each of these fibrils is seen to be crossed 

 with lines, represented in figure 233, plate 8. 

 These lines indicate the point of union of the 

 string of cells which form the ultimate parts of the 

 muscular tissue. 



The structure of nervous tissue is also one of 



