I. 



METHODS. 



riTHE methods of preparation of the liquid and solid constit- 

 JL uents of the animal body are of the utmost importance. 

 Every progress in histology is largely due to an improvement in 

 the methods of preparation employed as well as of the optical 

 apparatus. 



The main purpose obviously must be to examine liquids and 

 tissues in a condition as nearly as possible like that in which 

 they exist within the living body. The history of histology 

 teaches that the greatest errors have resulted from a neglect of 

 this rule. From the moment a specimen for examination with 

 the microscope is allowed to dry, such a specimen has become a 

 mummy, and unfit for further research. Almost all tissues, in 

 former times, were allowed to dry before their minute structure 

 was examined. The results of such researches are considered 

 worthless nowadays. Despite of all experience gained in the 

 last four decades, that is, the time in which microscopic mor- 

 phology has gradually developed into a science, even in our 

 day, dry bone-tissue is examined in all laboratories ; but such 

 examinations are necessarily of very small value. Another 

 objectionable procedure is the tearing, teasing, and pulling of 

 tissues. By such methods, the parts which in the body are 

 connected become broken and disfigured, debris are produced, 

 sometimes with the greatest skill, which, as a matter of fact, 

 are useless for fruitful microscopic investigations. Both me- 

 chanical and chemical isolation of the constituent parts of tissues 

 should be used to a very limited degree only. Just as objection- 



