HISTOLOGY 



CHAPTER I 

 PROTOPLASM 



AN outline of the discoveries which have led us to our present views 

 of life phenomena would not have the logical sequence of the method by 

 which these same facts can be unfolded to the student of to-day. Know- 

 ing first only the axiom that living things lived, attention was first drawn 

 to the hollow cell-like structure of plants; and animals were supposed 

 to be likewise constructed. Following this, we came to know the more 

 important fact that a semifluid content of these cells was a specific sub- 

 stance and was the fundamental life-material in living beings. Proto- 

 plasm was the name given this substance. 



Working forward again, we learned of the organization of this pro- 

 toplasm into the protoplast or solid living occupant of Schleiden and 

 Schwann's "cell," with which its name is so hopelessly entangled that 

 we must drop the better term here and use the hollow title of "cell" 

 for the life unit from this point on. 



Science was now free to branch out into many wide fields and with 

 much correction of error and understanding of truth to build up our 

 present accumulation of facts which, when compared with the great 

 truths we feel must really exist, is very small. That these truths hinge 

 primarily upon protoplasm, and consequently upon the cell, the tissue, 

 the organ, and lastly upon the individual, gives us an assurance of the 

 fundamental character and importance of our study of histology which 

 deals with the first three of these fields. 



Protoplasm, then, is our beginning, and we find first that it is present 

 in all life forms and that the life manifestations occur through the working 

 of its substance only. It is a transparent, viscid material to the sight and 

 touch and makes up a considerable part of a plant or animal body ; not 

 all necessarily, as more or less of such a body is built up of other and 

 non-living substances, which, however, are controlled entirely by the 

 living protoplasm. 



Of next greatest interest is perhaps the question, What is protoplasm 

 composed of chemically, and how is it put together structurally? A 

 qualitative analysis shows us that four out of the many known elements 



