204. IVAN E. WALLIN 
ing the fundamental properties of mitochondria. Attempts have 
been made to investigate their physiological properties, but 
aside from a possible relationship to chloroplast formation in 
plants, nothing definite, apparently, has been established con- 
cerning their function. Regarding the chemistry of mitochondria 
investigators generally agree that they are of the nature of phos- 
pholipins and lipoids and perhaps contain some albumin. The 
theory of their chemical nature is based on their reactions to 
staining methods and various chemicals. ‘Artificial mitochon- 
dria’ were produced by Léwschen (713) by the use of lecithin in 
different salt and albumin solutions. 
Considerable study has been given to the morphology of 
mitochondria. The result of this type of work has led to the 
conclusion by Cowdry (18) and others that the form of mito- 
chondria is variable and after all of little importance. Two 
forms of mitochondria predominate, namely, rod-shaped and 
globular forms. Besides these two predominating types various 
irregular forms may be found. 
An important consideration in the demonstration of mito- 
chondria is the technique. This technique warns to the exclusion, 
in the chemicals employed, of various solvents of mitochondria, 
chief of which are ether, alcohol, and acetic acid. It has not 
been claimed for the majority of mitochondria staining methods 
that they are specific for mitochondria. This ‘specificity,’ ap- 
parently, has reference to other materials in the cell. However, 
it must be assumed that these methods, if they are to be of value, 
must have a relative specificity for mitochondria. The janus 
green vital staining method has been definitely placed in a class 
of specific stains for mitochondria by Cowdry (18, p. 48). 
The striking resemblance of mitochondria to bacteria is ap- 
parent to all who are familiar with the two groups of structures. 
This resemblance has been noted by various authors and has 
led Cowdry to suggest a division of mitochondrial literature into 
two periods: an older literature in which mitochondria were 
observed in cells and mistaken for bacteria and a newer literature 
in which they have been observed and recorded under various 
names. 
