Fig. 82.—Félix Dujardin, 1801-1860.
No portrait of Dujardin was obtainable prior to 1898. Somewhat earlier Professor Joubin, who succeeded other occupants of the chair which Dujardin held in the University of Rennes, found in the possession of his descendants a portrait, which he was permitted to copy. The earliest reproduction of this picture to reach this country came to the writer through the courtesy of Professor Joubin, and a copy of it is represented in Fig. 82. His picture bespeaks his personality. The quiet refinement and sincerity of his face are evident. Professor Joubin published, in 1901 (Archives de Parasitologie), a biographical sketch of Dujardin, with several illustrations, including this portrait and another one which is very interesting, showing him in academic costume. Thanks to the spread of information of the kind contained in that article, Dujardin is coming into wider recognition, and will occupy the historical position to which his researches entitle him.
It was while studying the protozoa that he began to take particular notice of the substance of which their bodies are composed; and in 1835 he described it as a living jelly endowed with all the qualities of life. He had seen the same jelly-like substance exuding from the injured parts of worms, and recognized it as the same material that makes the body of protozoa. He observed it very carefully in the ciliated infusoria—in Paramœcium, in Vorticella, and other forms, but he was not satisfied with mere microscopic observation of its structure. He tested its solubility, he subjected it to the action of alcohol, nitric acid, potash, and other chemical substances, and thereby distinguished it from albumen, mucus, gelatin, etc.
Inasmuch as this substance manifestly was soft, Dujardin proposed for it the name of sarcode, from the Greek, meaning soft. Thus we see that the substance protoplasm was for the first time brought very definitely to the attention of naturalists through the study of animal forms. For some time it occupied a position of isolation, but ultimately became recognized as being identical with a similar substance that occurs in plants. At the time of Dujardin's discovery, sarcode was supposed to be peculiar to lower animals; it was not known that the same substance made the living part of all animals, and it was owing mainly to this circumstance that the full recognition of its importance in nature was delayed.
The fact remains that the first careful studies upon sarcode were due to Dujardin, and, therefore, we must include him among the founders of modern biology.
Fig. 83.-Purkinje, 1787-1869.
Purkinje.—The observations of the Bohemian investigator Purkinje (1787-1869) form a link in the chain of events leading up to the recognition of protoplasm. Although Purkinje is especially remembered for other scientific contributions, he was the first to make use of the name protoplasm for living matter, by applying it to the formative substance within the eggs of animals and within the cells of the embryo. His portrait is not frequently seen, and, therefore, is included here (Fig. 83), to give a more complete series of pictures of the men who were directly connected with the development of the protoplasm idea. Purkinje was successively a professor in the universities of Breslau and Prague. His anatomical laboratory at Breslau is notable as being one of the earliest (1825) open to students. He went to Prague in 1850 as professor of physiology.
