DISCOVERY OF THE PROTOZOA 107 
one of the early observers of nerve fibres and of many other 
structures of the animal frame. His book of the protozoa 
is a beautifully illustrated monograph consisting of 532 pages 
of letterpress and 69 plates of folio size. It was published in 
1836 under the German title of Die Injusionsthierchen als 
Vollkommene Organismen, or “The Infusoria as Perfect Or- 
ganisms.” The animalcula which he so faithfully represented 
in his sketches have the habit, when feeding, of taking into 
the body collections of food-particles, aggregated into spher- 
ical globules or food vacuoles. These are distinctly sepa- 
rated, and slowly circulate around the single-celled body while 
they are undergoing digestion. In a fully fed animal these 
food-vacuoles occupy different positions, and are enclosed in 
globular spaces in the protoplasm, an adjustment that gave 
Ehrenberg the notion that the animals possessed many 
stomachs. Accordingly he gave to them the name ‘ Poly- 
gastrica,” and assigned to them a much higher grade of 
organization than they really possess. These conclusions, 
based on the general arrangement of food globules, seem 
very curious to us to-day. His publication was almost simul- 
taneous with the announcement of the cell-theory (1838-39), 
the acceptance of which was destined to overthrow his con- 
ception of the protozoa, and to make it clear that tissues and 
organs can belong only to multicellular organisms. 
Ehrenberg (Fig. 31) was a man of great scientific attain- 
ments, and notwithstanding the grotesqueness of some of his 
conclusions, was held in high esteem as a scientific investi- 
gator. His observations were accurate, and the beautiful 
figures with which his work on the protozoa is embellished 
were executed with such fidelity regarding fine points of 
microscopic detail that they are of value to-day. 
Dujardin, whom we shall soon come to know as the dis- 
coverer of protoplasm, successfully combated the conclusions 
of Ehrenberg regarding the organization of the protozoa. 
