236 On Cell Life. [April, 
I would remind the reader of the opinion of a well-known labourer in 
the minute structure of the tissues, Professor Frey, of Zurich, who 
says of cells, in his ‘Handbook of Microscopie Anatomy, “they 
represent living beings, both as regards their anatomical and 
physiological individuality.” But what is a cell? ‘To this 
question it is by no means easy to give a reply. A full and 
clear definition of a cell is not yet possible. Let us try, by 
the help of observation and dissection, to form an idea of the 
nature of a cell. It is well known that the organs of animals 
and of plants do not consist of a homogeneous mass, but are formed 
of separate parts which have definite forms and properties. The 
elementary components of one of the higher animals or plants are 
various in their character, as the microscope teaches us. Many 
tissues consist of solid filaments, others of pipes or tubes, which are 
filled with contents readily distinguishable from the tube-walls. 
These elementary parts may exhibit, in their fully developed con- 
dition, great variety and differences, but in the earliest stages of 
development they are not distinguishable from one another. 
Where a tissue is about to be developed, a number of small 
bodies are observable from the commencement, always wonderfully 
alike in form. They appear to be rounded lumps of a thick shmy 
substance ; somewhere in the inside of each lump there is a clear, 
well-defined, and somewhat transparent globule, with a dark spot 
in the middle. Such a body as this is called, in the restricted 
meaning of the word, ‘a cell;’ the transparent globule within it, 
‘a nucleus;’ and the dark spot in the middle of the globule, ‘the 
nucleolus. The formation of the most complex tissues of the 
animal body takes place in the following manner only: The 
original component cells multiply themselves. This multiplication 
takes place (as far as sound observations have ascertained) entirely 
by the subdivision of the mother cells, a process which is continually 
going on; the nuclei divide so as to separate the nucleoli into 
halves, and the surrounding material draws itself together into 
two masses around each of the newly-formed nuclei, and at last the 
masses become detached from one another. 
Connected with the preceding statement, there is a most 
important question, relating to our knowledge of organic nature, in 
regard to which a lively contest has lately been renewed. The 
question is, whether individual creations of organic beings occur. 
Here the problem comes before us in a still more general form— 
namely, are there special creations of cells. The most reliable 
observers at the present day are agreed that the creation of a cell 
in an animal tissue has never yet been seen with certainty, and that 
each cell is the offspring of another, from which it has separated 
by division. Here, then, we have already decided evidence that the 
cell is to be regarded as an organic individual. 
