106 HOW TO WORK 



at if balsam specimens only are submitted to examination. In 

 figs. 165 and 1 66, pi. XXV, specimens of the very same tissue 

 are represented prepared according to the different plans referred 

 to, but magnified by the same powers. Let the reader observe the 

 different diameter of the vessels and note how many points are dis- 

 played in the moist preparation which are not to be demonstrated in 

 the one preserved in balsam. I feel, therefore, compelled to reject 

 inferences arrived at from the examination of balsam specimens, and 

 strongly advise the student not to be misled by their mere sharpness 

 and bright colour. Such preparations undoubtedly enable us to form 

 a general idea of the arrangement and number of the capillaries in 

 different textures, and in this respect are of value, but they are use- 

 less if we wish to learn facts concerning the relation of the capillaries 

 to the texture lying in their meshes, the structure of the vessels them- 

 selves, or that of the tissues in which they ramify. 



195. Of the best Mode of Destroying the Life of Animals intended 

 for injection. I have tried various plans of destroying animals in- 

 tended for minute injection, and have found that in death by sudden 

 shock the vessels remain in a relaxed state for a sufficient time after 

 death to enable us to complete the injection. In some cases a good 

 result is gained by destroying life in an atmosphere of carbonic acid, 

 but I find that the very sudden death produced by a fall from a 

 height, dashing on the ground, &c., is the most advantageous. Any 

 small animal may be wrapped up in a cloth and thrown suddenly 

 and with some force upon the ground. In order to avoid rupturing 

 any of the tissues the animal must be protected by several folds of 

 the cloth. Swinging very rapidly through the air also destroys life 

 very suddenly, without causing that sudden contraction of the muscles, 

 which seriously interferes with successful injection. 



Good injections may be made after the rigor mortis has entirely 

 passed off, and formerly no attempt was made to inject before this 

 period. But when the muscles have again become relaxed the finer 

 branches of the nerves will be found softened or entirely destroyed, 

 and many delicate structures so much altered that it would not be 

 possible for any one who was acquainted with their natural appear- 

 ance to recognise them. Hence it is useless to put off the operation 

 of injection if we desire to demonstrate in the specimens more than 

 the arrangement of the capillaries only. 



