All agree that the turning point iii the development of our knowledge of mitochondria was the discovery reported by Bensley and Hoerr in 1934, that mitochondi’ia, by washing and by centrifugation, (‘all I)e separated from other cytoplasmic components and collected in adequate amounts for chemical analysis. It is my privilege briefly to sketch what we learned about mitochondria before the utilization of this technique as a background for the presentation of the most recent discoveries by others in this symposium. When I first came under the influence of Dr. Bensley at the University of Chicago about 43 years ago, he was already a leader in the investigation of mitochondria. I have 1)een his devoted follower ever since. He often referred us to the historical classic on mitochondria, a beautifully illustrated book by Altmann, published first in 1890. Altmann was well trained in physics and chemistry. His long series of experiments were carefully planned and his results were recorded with meticulous accuracy. It has been the lot of several investigators to report findings only to discover that they had repeated, rather less accurately, Altmann’s work. But he became impressed with the morphological resemblance between mitochondi’ia and h)acteria and called them “l)iol)lasts” (flL6s, life; f3Xa rbs, germ) to indicate his belief that they were elementary vital units existilIg in all cells. This view was received with scant tolerance by others in Germany. At that time the late Prof. F. P. Mall was also working in Leipzig. He described Altmann and his mental state in a graphic way. The idea of bioi)lasts dominated Altmann’s whole being. He would not brook criticism, used to slink into the laboratory by the l)ack door and was called “der Geist”, the ghost. Things went from bad to worse and the end was tragic and of the sort expected. But Bensley was not led astray by the hioblast hypothesis. He fully appreciated the value of Altmann’s objective findings for they revealed the existence of granules, rods and filaments that did resemble bacteria superficially in many different kinds of celis-in other words the presence of fundamental and intriguing cytoplasmic components. Another example of Bensley’s vision i-elates to the description by Michaehs (1899) and Laguesse (1900) of similar structures stained with ,Janus green ill fresh living cells. While others paid no attention to these observations, Bensley studied the paper of Michaelis carefully and noted that the kind of .Janus green advised by Michaelis was the diethyl compound. This he obtained and with it introduced the best technique for the examination of mitochondria in still living cells. Knowing exactly what to look for, he had no difficulty in seeing them in