Minot.] 202 [April 2, 
General Meeting. March 19, 1879. 
The President, Mr. T. T. Bouvé, in the chair. Seventeen 
persons present. 
Dr. B. Joy Jeffries read a paper on various phenomena of 
color blindness and color perception. 
Prof. P. F. Reinsch described some supposed microscopic 
organisms, observed in slate from low strata of Silurian 
formation in Illinois, and from the anthracite coal of Penn- 
sylvania. 
General Meeting. April 2, 1879. 
The President, Mr. T. T. Bouvé, in the chair. Forty-three 
persons present. 
The following papers were read : 
PRELIMINARY NOTICE OF CERTAIN LAWS OF HISTOLOGICAL 
DIFFERENTIATION. By CHARLES SEDGWwickK MINOT. 
The following article contains certain results, which I think may 
be safely deduced from various data, familiar to histologists. It has 
been my effort to formulate such general laws relating to the pro- 
cesses of histological differentiation, as I could gather either from 
the writings of others or from my own studies. Some of the con- 
clusions thus formulated, I now publish in the hope that they may 
prove of some interest and value to others. 
1. The most primitive form of tissue is an epithelium composed of a 
single row of polyhedral cells of equal height. It is well known 
that the two germinal layers in all animals, in which they have been 
studied, first appear as simple epitheliums. There is in the em- 
bryonic life of many invertebrate animals a stage, during which the 
whole body consists solely of epithelial tissues. In the primitive 
epithelium the cells when viewed from the surface are always irreg- 
ular in outline, and usually 5-6 sided, sometimes 7 (or perhaps 
more) sided, but probably never four-sided, except occasionally 
isolated cells which assume that outline. There is a round or nearly 
round nucleus in the central part of each cell. In every epithelial 
cell three axes may be distinguished, two parallel and one perpen- 
Sa ee ee ee eee 
