Chabry’s Capillary Object Holder (1887)

Chabry’s “capillaire porte-object” (capillary object holder) was among the earliest instruments that can be considered a micromanipulator. Developed for use in experiments on the development of the eggs of Ascidiella aspersa, a species of sea squirt, the instrument held the sample in a glass pipette that could be rotated for convenient observation. It also incorporated a spring-loaded glass microneedle for piercing the sample.

The capillary object holder was introduced in a paper by the French biologist Laurent Chabry (1855-1893) who was then working at the Marine Biological Laboratory at Concarneau in Brittany—a location that permitted him to harvest eggs of A. Aspersa which were the subject of his paper. Chabry used his instrument to observe and manipulate marine embryos in the very early stages of development.

Chabry was especially interested in the abnormal segmentation of the embryo up to the thirty-two cell stage. He recovered naturally occurring mutant eggs and introduced abnormalities into healthy ones using a “perforator” to selectively damage or destroy individual blastomeres within the developing egg. He then observed the consequences for development.

Chabry created his instrument for this purpose, though he also claimed that it was broadly useful:

I insist on the commodiousness of this little apparatus; all those who will make use of it will be surprised by the ease that it brings to all types of observation. We can, with its aid, immediately view any point of the anatomy of small animals that is visible on the living organism through obtaining an immediate, sure and perfect, orientation. The examination of fixed and dyed objects is equally easy, and one can mount permanent preparations in capillaries. [Chabry 1887, 175]

Both the capillary object holder and the perforator are illustrated in this diagram:

Chabry Capillary Object Holder

An illustration of Chabry’s instrument. The protective sheath, illustrated below, is not depicted. [Chabry 1887, 174]

The Capillary Object Holder

The base of the instrument consisted of a sturdy piece of plate glass. The sample was contained in a glass pipette (“T”) that was held in place along the long dimension of the base by two glass guides (“d”)—fragments of a slightly larger pipette—that were cemented to the base. The pipette slid along, and rotated within, these guides. One end of this pipette, which extended beyond the microscope stage, had a horizontal branch attached to it. This permitted the sample to be rotated using a simple apparatus that bolted to the microscope base through one of the holes normally used for slide clips. This was turned by a little wheel.

The Perforator

The perforator consisted of a spring-loaded glass microneedle which Chabry refers to as un dard—literally a “stinger”—that fit within the capillary holding the sample. Chabry’s paper provided the earliest method for creating this type of tool by putting a very fine point on a narrow glass pipette.

The needle had to travel quickly enough to penetrate the egg rather than simply pushing it away. It also had to be stopped abruptly so that it did not travel all the way through the egg and destroy it. This was accomplished using a spring consisting of a brass wire “R” which abutted a lever connected to one end of the needle. The travel of the needle was adjusted and limited using an threaded screw and a nut/ stop that attached to the microscope (“E”). This stop acted essentially as a micrometer adjustment, permitting the operator to advance the needle just to the surface of the egg. By setting the spring and advancing the stop slightly, the needle could be made to destroy a single blastomere within the egg. [Chabry 1887, 175-178]

The capillary object holder and the perforator were joined by a protective sheath (une gaîne protectrice) that sheltered the delicate point, guided the perforator into the capillary containing the sample, and permitted the capillary to be removed and replaceddue to their sensitivity, eggs could only be observed for 10 minute intervals two to three times per day. This sheath is labelled “G” in the illustration below.

Chabry Holder 2

Two capillary object holders built for embryos of different sizes. [Chabry 1887, 179]

As this illustration indicates, one characteristic of Chabry’s instrument was that the internal diameter of the capillary had to conform very closely to the size of the sample in order to properly rotate it. Much of the rest of the instrument also had to be scaled in proportion. For instance, an instrument used with an A. Aspersa embryo could not be used with a much smaller sea urchin embryo. [Chabry 1887, 173]

From Chabry’s description it seems that much of the instrument, except perhaps the adjustable stop and the spring, could be made by an operator with typical knowledge of laboratory glasswork. I don’t know, at this point, how widely this apparatus was used or how this type of instrument subsequently evolved. Any information would be appreciated.

Bibliography

 

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