describing now the drawings , for the analysis an appropriately prepared sample of a liquid containing erythrocytes and leucocytes is conducted through a feeling or scanning zone , wherein the feeler or scanner means can be designed for instance to be electrical or optical in nature . the particles suspended in the liquid are scanned during their passage through the scanning zone , and the scanned particles generate suitable pulses or signals of different characteristics or properties as a function of the physical characteristics of the sampled particle types . during the analysis of leucocytes the advantageous preparation of the sample , among other things , resides in removing the erythrocytes by means of hemolysis and which erythrocytes are typically present in a 1000 - fold higher concentration . during this treatment the erythrocytes are specifically destroyed and there is now present in the solution to be examined a many thousand - fold higher concentration of cell fragments of the destroyed erythrocytes in relation to the morphologically altered but intact leucocytes . these fragments form , or should form , a different size class than the leucocytes ; coarsely considered there is present a bimodal mixed distribution . in the ideal case the distribution of the artifacts , in this instance the fragment particles , is well separated from the distribution of the leucocytes and a separation of both distributions by a separation threshold leads to a truncated distribution of the leucocytes with an extremely small degree of truncation ; a subsequent correction therefore can be dispensed with . practical experience has shown that results from an uncorrected , truncated distribution are also usable with markedly overlapping mixed distributions . thus , for instance , during erythrocyte analysis , the deviation from an approximate normal distribution constitutes evidence as to a certain pathological change and in graphical portrayal can be used as a further result of the analysis . the consequence of this is that : classes having marked deviation from the normal distribution cannot be positively corrected even when incorporating into the analysis usually complicated computation procedures . the result from a truncated distribution together with a quality criterion , for instance the amplitude of the threshold value , is easier to judge than an inadequately corrected result . thus , in practice , there is normally dispensed with a correction of the truncated distribution . in fig1 there is shown a block diagram of a particle counter a with the related feeler or sensor element a &# 39 ;, which for ease in illustration has been shown immersed in a particle sample c which is to be examined . the signal line 50 between the feeler element a &# 39 ; and the particle counter a is tapped - off by the infeed line 41 leading to the auxiliary apparatus b , in order to infeed the electrical particle signals to such auxiliary apparatus b . an operating device 100 allows performance of the requisite manipulations for setting the desired threshold . the particles in the range of the threshold are counted and the counting result is infed by means of the infeed line 81 for further evaluation to the particle analyser a . of course , the auxiliary apparatus b can be physically incorporated within the particle counter a , so that several of the components illustrated in fig3 perform a dual function . for instance , the pulses appearing at the line 71 ( fig3 ) can be infed to a pulse counter located in the particle analyser . a switching device 5 at the auxiliary apparatus b ( fig1 ) enables , as a further operating element , switching from the operating mode &# 34 ; finding thresold &# 34 ; to the operating mode &# 34 ; particle counting ,&# 34 ; under which there is meant the counting and display of a particle class which is to be entirely determined . the operation of the operating device 100 has been shown in fig2 a and the operation of the switching device 5 in fig2 b . fig2 a illustrates a typical bimodal size class distribution having a relatively clearly discernible or pronounced transition from one size class to the other . related to the example of leucocyte analysis , the not completely illustrated distribution of the class e is predicated upon the hemolyzed erythrocytes , in other words their fragments , while the distribution of the class l is predicated upon the intact leucocytes . the cell fragments of the erythrocytes as particles , intentionally , form a class having a mean value of the particle size which is clearly smaller than the mean value of the intact leucocytes . thus , the artifacts ( erythrocyte fragments ) can be separated from the leucocytes where are to be analysed by setting a threshold . the threshold value is now set at the lowest point in the valley between both classes . as already previously explained , this is accomplished either in indirect form by means of a summation distribution curve or in direct form with the aid of an oscilloscope , in the latter case without counting , predicated upon a visual impression of a minimum pulse count of those pulses which project past the simultaneously displayed pulses of the &# 34 ; artifact noise .&# 34 ; it is well known that a human being is most capable of determining the number of elements of a quantity when such are present in an explicit form ( for instance the human can readily imagine the quantitative value for instance in the form of a value such as 500 screws per box ). the invention proceeds from this recognition and delivers for the separation threshold a numerical value instead of the heretofore usual diagrammatic portrayal . according to fig2 a and also fig2 b the particle quantity per volume unit of the sample at the valley between both distributions , in other words between both of the thresholds v 1 and v 2 , is smallest . now if by means of the selector switch or reversing switch means 5 the difference v 2 - v 1 is made very small , i . e . the particle size range should be small , which here corresponds to the positions of fig2 a , and thereafter with the aid of the operating device 100 the thresholds v 1 and v 2 are simultaneously shifted or displaced over the particle volume range -- indicated by a double - headed arrow --, then it is possible to perform at arbitrarily chosen positions a brief particle counting of volumes which each time are of equal size ; the determined count is directly indicated in a display . this corresponds to the explicit representation of the counted elements of a quantity . in practice for such type counting there is needed only a few seconds . by systematically shifting and counting in the direction of smaller count values there is determined the valley base extremely quickly , positively and with very slight observation expenditure on the part of the operator , i . e ., the location where the fault due to truncation is lowest . with increasing experience in handling the auxiliary apparatus it is possible to observe the count rate ( particle / time unit ) while shifting the threshold pairs v 1 , v 2 during the counting operation ; in this way it is possible to further reduce the time needed for finding a threshold . thereafter , by means of the reversing switch means or selector switch 5 the threshold v 2 is shifted through such a magnitude that , as determined by empirical values or experience , it encompasses the distribution of the leucocytes ( fig2 b ) and there can be carried out an analysis count . for improved clarity in illustration both of the thresholds v 1 and v 2 have been shown in fig2 a spaced unrealistically far apart from one another , and for this reason also the lower discriminating threshold v 1 in fig2 b appears to be shifted into the artifact region . if there is desired , for instance , a further increased accuracy of the threshold position , then by means of an additional switch contact in the line or conductor leading to the first comparator it is possible , by means of a further comparison voltage , to shift the threshold v 1 -- simultaneous with the shifting of the threshold value v 2 -- by the half magnitude v 2 - v 1 in the direction of greater particle volume sizes . if the threshold has once been set at the start of an analytical measurement series , then during each new measurement of blood samples of the same species , it is possible to determine within seconds whether the threshold has been placed at the proper position or whether there is required a correction . as a further auxiliary means or aid for setting the threshold at the start of a measuring series with unknown distribution it has been found to be advantageous to use a simultaneous acoustical indicator , for instance a small loudspeaker , during the systematic displacement or shifting of the threshold pair in the direction of lower counting values . the effect is similar to that encountered with a geiger counter , there is produced an integral impression of the quantity of the particle pulses and together with the explicit quantity display or indication there is obtained a redundancy which is favorable for the measurement reliability . the already mentioned minimization of the counting rate is further facilitated with the aid of this acoustical indicator . finally , in fig3 there is shown in block circuit diagram the interconnection of the different circuit components , which components are conventional and thus need not be described here in detail they are well known in the electronics art . by referring to fig3 there will be recognized a first comparator 1 having an infeed line or conductor 41a leading from a feeler or sensor element 40 and receiving the electrical signals which are generated by such feeler element 40 . the comparator 1 also is provided with an infeed line 11 carrying a first comparison voltage or potential which is produced by the means 10 for generating such first comparison voltage . there is also provided a second comparator 2 having an infeed line 41b connected with the feeler 40 for receiving the electrical signal generated by the feeler or feeler element 40 . the comparator 2 also has further infeed lines or conductors 21a , 21b which receive a second comparison voltage or potential from the means 20 which generate such second comparison voltage . there are also provided means 100 for the simultaneous variation of the first comparison voltage and the second comparison voltage by the same amount or magnitude , and means 30 for generating a third comparison voltage . a switch or reversing switch means 5 is arranged at the infeed lines or conductors 21a , 21b carrying the second comparison voltage and leading to the second comparator 2 for switching to the infeed lines or conductors 31 , 21a leading from the means 30 which generate the third comparison voltage . reference character 6 designates means for delaying the output signal appearing at the line or conductor 12 at the output side of the first comparator 1 , and reference character 7 constitutes an antivalence discriminator means having an infeed line or conductor 61 leading from the time - delay element or means 6 and a further infeed line or conductor 22 leading from the second comparator 2 . finally , there is provided a pulse counter 8 having an infeed line or conductor 71 leading from the output side of the antivalence or exclusive - or discriminator 7 . while there are shown and described present preferred embodiments of the invention , it is to be distinctly understood that the invention is not limited thereto , but may be otherwise variously embodied and practiced within the scope of the following claims . accordingly ,