An economical, semi-automatic system for measuring cellular tree structures in three dimensions, with special emphasis on Golgi-impregnated neurons.

The hardware and software of a semi-automatic system are described for the measurement of cellular tree structures in thick microscopical sections such as the process of Golgi-impregnated neurons. With this system, the morphologist--viewing the neuron directly through the microscope--measures the tree structures using three cartesian coordinates of characteristic points, e.g. centre of cell, origin of processes, bifurcation points, end points, deflection points, etc. The system requires an on-line computer, but does not demand a dedicated computer since a joy-stick generator usually drives the microscopical stage during cell tracking. A digital computer is utilized for acquisition of data, and, when needed, to return the stage to a required position. The microscope stage is coupled to three stepping motors with 0.5 micron as the smallest step. The stepping motor for movement of the stage parallel to the optical axis (z-direction) is coupled directly to a spindle mechanism, replacing the original cog wheel mechanism. This construction shows no measurable backlash. The practical advantages of this new measuring system in relation to the existing digital systems currently in use, its accuracy and its costs, are discussed.